Add apex salesforce library

Using-the-API/API.md

@@ -43,6 +43,7 @@ ___
 |-------|--------|------------|
 | .Net | [Mastodon.Net](https://github.com/Tlaster/Mastodon.Net) | |
 | .NET Standard | [Mastonet](https://github.com/glacasa/Mastonet) | |
+| Apex(Salesforce) | [apex-mastodon](https://github.com/tzmfreedom/apex-mastodon) | |
 | C# | [mastodon-api-cs](https://github.com/pawotter/mastodon-api-cs) | |
 | C#(.NET Standard) | [Mastodot](https://github.com/yamachu/Mastodot) | |
 | Crystal | [mastodon.cr](https://github.com/decors/mastodon.cr) | |