Update "README.md": Add 1.21.9 - 1.21.11 to the "Supported versions" section

Author: JDDev0

README.md

@@ -176,7 +176,7 @@ A tutorial world showcasing all the features of this mod can be downloaded on Cu
 
 ## Supported versions:
 Mod version: MC version
-- 2.15.x: 1.21.8, 1.21.1, 1.20.1
+- 2.15.x: 1.21.11, 1.21.10, 1.21.9, 1.21.8, 1.21.1, 1.20.1
 - 2.14.x: 1.21.8, 1.21.7, 1.21.6, 1.21.5, 1.21.1, 1.20.1
 - 2.13.x: 1.21.5, 1.21.4, 1.21.1, 1.20.1
 - 2.12.x: 1.21.4, 1.21.3, 1.21.2, 1.21.1, 1.21, 1.20.2, 1.20.1, 1.19.2