docs: September 2019 Documentation Update (#1379)

* docs: adjust wording of ActivityType.Watching enum

Adjusts the xmldoc summary wording of the ActivityType.Watching enum to
fix a wording issue.

* Add D.NET Logo to Open Graph meta tags

* Update DescriptionGenerator
...And update color to suit the logo better

* Disable smooth scrolling due to user complaints

* Remove unnecessary spacing in sideaffix

* Update footer version

* Remove featherlight plugin

As it is unnecessary and can break image tags

* Adjust wordings regarding safe-handling of secrets

* Fix formatting for first bot token sample

* Add badges to homepage

* Minor wording fixes on terminal

* Update to higher quality PNG

* Add Discord.Net.Example in sln for build validation

* Clarify all instances of IAsnycEnumerable

* Clarify overridden props in SocketNewsChannel

* Add returns and params docs for SyncPermissionsAsync

* Remove/fix invalid XMLdoc strings

* Remove AppVeyor and add GitHub badge

docs/_template/light-dark-theme/styles/master.css

@@ -6,7 +6,6 @@ body {
     font-display: optional;
     height: 100%;
     font-size: 15px;
-    scroll-behavior: smooth;
 }
 
 code{
@@ -92,6 +91,10 @@ article.content h6{
     line-height: 140%;
 }
 
+.sideaffix > div.contribution {
+    margin-bottom: 0;
+}
+
 header .navbar {
     border-width: 0 0 0px;
     border-radius: 0;