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>

docs/guides/getting_started/nightlies.md

@@ -31,22 +31,33 @@ The following is the feed link of Discord.Net,
 Depending on which IDE you use, there are many different ways of
 adding the feed to your package source.
 
-### [Visual Studio](#tab/vs)
+### [Using Visual Studio](#tab/vs)
 
 1. Go to `Tools` > `NuGet Package Manager` > `Package Manager Settings`
+
     ![VS](images/nightlies-vs-step1.png)
+
 2. Go to `Package Sources`
+
     ![Package Sources](images/nightlies-vs-step2.png)
+
 3. Click on the add icon
 4. Fill in the desired name and source as shown below and hit `Update`
+
     ![Add Source](images/nightlies-vs-step4.png)
 
 > [!NOTE]
-> Remember to tick the `Include prerelease` checkbox to see the
+> Remember to tick the `Include pre-release` checkbox to see the
 > nightly builds!
 > ![Checkbox](images/nightlies-vs-note.png)
 
-### [Local NuGet.Config](#tab/local-nuget-config)
+### [Using dotnet CLI](#tab/cli)
+
+1. Launch your terminal
+2. Navigate to where your `*.csproj` is located
+3. Type `dotnet add package Discord.Net --source https://www.myget.org/F/discord-net/api/v3/index.json`
+
+### [Using Local NuGet.Config](#tab/local-nuget-config)
 
 If you plan on deploying your bot or developing outside of Visual
 Studio, you will need to create a local NuGet configuration file for