Remove AppVeyor and add GitHub badge

docs/index.md

@@ -7,6 +7,7 @@ title: Home
 
 <div class="big-logo logo-switcher"></div>
 
+[![GitHub](https://img.shields.io/github/last-commit/discord-net/discord.net?style=plastic)](https://github.com/discord-net/Discord.Net)
 [![NuGet](https://img.shields.io/nuget/vpre/Discord.Net.svg?maxAge=2592000?style=plastic)](https://www.nuget.org/packages/Discord.Net)
 [![MyGet](https://img.shields.io/myget/discord-net/vpre/Discord.Net.svg)](https://www.myget.org/feed/Packages/discord-net)
 [![Build Status](https://dev.azure.com/discord-net/Discord.Net/_apis/build/status/discord-net.Discord.Net?branchName=dev)](https://dev.azure.com/discord-net/Discord.Net/_build/latest?definitionId=1&branchName=dev)
@@ -25,8 +26,3 @@ If this is your first time using Discord.Net, you should refer to the
 More experienced users might want to refer to the
 [API Documentation](xref:API.Docs) for a breakdown of the individual
 objects in the library.
-
-## Additional Resources
-
-- [GitHub](https://github.com/discord-net/Discord.Net/)
-- [AppVeyor CI](https://ci.appveyor.com/project/RogueException/discord-net) - Nightly builds via Continuous Integration