docs: Main docs update (#1304)

* Remove template in favor of official samples

* Fixed a variable name copy pasta mistake

line 35 was _database.GetData() instead of DBService.GetData()

* Experimental theme change

* Change paragraph, code, heading fonts
* Widen viewport

* Update DocFX.Plugins.LastModified v1.2.3

* Exclude Discord.API in docs

* Add remarks for SocketReaction properties

* Add examples for BaseSocketClient.Events

* Add additional clarification for some methods

* Move IUser and IGuildChannel examples

* Clarify several guides samples with notes

- Reword TypeReader comment to avoid giving the idea that the sample itself is "obsolete"
- Remove CommandException logging comment regarding C#7.0 as the version is now the standard across VS2017 and up
- Remove suggestion about handling result in command handler since it is now advised to use CommandExecuted instead
+ Add additional comment to clarify ctor for DI setup

* Add/migrate code examples

* Incorporate material design theme

License @ https://github.com/ovasquez

* Update installation and nightly guide

* Fix improper indentations made obvious by the widen viewport
* Fix minor grammar issues
+ Add installation for nightly build using dotnet CLI

* Fix nav level indentation

* Revise "Your First Bot" article

* Merge some paragraphs to avoid clutter while keeping readability
* Reword the use of command framework
+ Add additional warning/note about environment variable

* Add additional indent level

* Fix indentation text warping

* Remove connections sample

* Update logging sample

Remove redundant part of the sample

* Remove mention of RPC

* Remove misleading section about commands

- Remove command sample from complete snippet
* Revise "Your First Bot" command paragraphs
* Change wording to hint devs that additional command parser packages may be available, as more and more begin to crop up

* Update themes

* Add XML docs contribution guidelines


Update guidelines

* Update CommandExecuted remarks

* Fix precondition remarks typo
no one saw that ok

* Fix permission sample in docfx

* Fix IMessageChannel samples

* Update docs/_template/light-dark-theme/styles/docfx.vendor.minify.css

Co-Authored-By: Still34 <341464@gmail.com>

* Update docs/_template/light-dark-theme/styles/material.css

Co-Authored-By: Still34 <341464@gmail.com>

* Update docs/_template/light-dark-theme/styles/material.css

Co-Authored-By: Still34 <341464@gmail.com>

src/Discord.Net.WebSocket/BaseSocketClient.cs

@@ -97,13 +97,15 @@ namespace Discord.WebSocket
         /// <remarks>
         ///     This method gets the user present in the WebSocket cache with the given condition.
         ///     <note type="warning">
-        ///         Sometimes a user may return <c>null</c> due to Discord not sending offline users in large
-        ///         guilds (i.e. guild with 100+ members) actively. To download users on startup, consider enabling 
-        ///         <see cref="DiscordSocketConfig.AlwaysDownloadUsers"/>.
+        ///         Sometimes a user may return <c>null</c> due to Discord not sending offline users in large guilds
+        ///         (i.e. guild with 100+ members) actively. To download users on startup and to see more information
+        ///         about this subject, see <see cref="Discord.WebSocket.DiscordSocketConfig.AlwaysDownloadUsers" />.
         ///     </note>
         ///     <note>
         ///         This method does not attempt to fetch users that the logged-in user does not have access to (i.e.
-        ///         users who don't share mutual guild(s) with the current user).
+        ///         users who don't share mutual guild(s) with the current user). If you wish to get a user that you do
+        ///         not have access to, consider using the REST implementation of
+        ///         <see cref="DiscordRestClient.GetUserAsync(System.UInt64,Discord.RequestOptions)" />.
         ///     </note>
         /// </remarks>
         /// <returns>
@@ -114,20 +116,22 @@ namespace Discord.WebSocket
         /// <summary>
         ///     Gets a user.
         /// </summary>
-        /// <param name="username">The name of the user.</param>
-        /// <param name="discriminator">The discriminator value of the user.</param>
         /// <remarks>
         ///     This method gets the user present in the WebSocket cache with the given condition.
         ///     <note type="warning">
-        ///         Sometimes a user may return <c>null</c> due to Discord not sending offline users in large
-        ///         guilds (i.e. guild with 100+ members) actively. To download users on startup, consider enabling 
-        ///         <see cref="DiscordSocketConfig.AlwaysDownloadUsers"/>.
+        ///         Sometimes a user may return <c>null</c> due to Discord not sending offline users in large guilds
+        ///         (i.e. guild with 100+ members) actively. To download users on startup and to see more information
+        ///         about this subject, see <see cref="Discord.WebSocket.DiscordSocketConfig.AlwaysDownloadUsers" />.
         ///     </note>
         ///     <note>
         ///         This method does not attempt to fetch users that the logged-in user does not have access to (i.e.
-        ///         users who don't share mutual guild(s) with the current user).
+        ///         users who don't share mutual guild(s) with the current user). If you wish to get a user that you do
+        ///         not have access to, consider using the REST implementation of
+        ///         <see cref="DiscordRestClient.GetUserAsync(System.UInt64,Discord.RequestOptions)" />.
         ///     </note>
         /// </remarks>
+        /// <param name="username">The name of the user.</param>
+        /// <param name="discriminator">The discriminator value of the user.</param>
         /// <returns>
         ///     A generic WebSocket-based user; <c>null</c> when the user cannot be found.
         /// </returns>