Add features to README.md

Author: Kiber2009

README.md

@@ -1,3 +1,13 @@
 | [Modrinth](https://modrinth.com/plugin/contentapi) | [Hangar](https://hangar.papermc.io/Kiber2009/ContentAPI) |
+
 # ContentAPI
-API for adding custom content
+API for adding custom content
+
+## Features
+- Registry system
+- Argument types for `com.mojang.brigadier`
+- Custom items
+- Custom recipes (WIP)
+  - Crafting
+
+See [wiki](https://github.com/Kiber2009/ContentAPI/wiki) for more information