Update Community_Resources.mdx to include the concord library (#7157)

* Update Community_Resources.mdx to include the concord library

Author: mazylol

docs/developer-tools/community-resources.mdx

@@ -14,6 +14,7 @@ Discord does not maintain official SDKs.  The following table is an inexhaustive
 
 | Name                                                          | Language   |
 |---------------------------------------------------------------|------------|
+| [Concord](https://github.com/Cogmasters/concord)              | C          |
 | [Discord.Net](https://github.com/discord-net/Discord.Net)     | C#         |
 | [DSharpPlus](https://github.com/DSharpPlus/DSharpPlus)        | C#         |
 | [D++](https://github.com/brainboxdotcc/DPP)                   | C++        |