Update project description in README.md

Author: Kiber2009

README.md

@@ -1,7 +1,7 @@
 | [Modrinth](https://modrinth.com/plugin/contentapi) | [Hangar](https://hangar.papermc.io/Kiber2009/ContentAPI) |
 
 # ContentAPI
-API for adding custom content
+API for adding custom content to PaperMC-based servers
 
 ## Features
 - Registry system