(#181) Correct docs

Author: colinangusmackay

docs/index.md

@@ -55,7 +55,7 @@ v1.x supports: .NET Core 3.1 and .NET 5.0
 
 v2.x supports: .NET 6.0, 7.0 and 8.0
 
-v3.x supports: .NET 6.0 and 8.0
+v3.x supports: .NET 6.0, 8.0 & 9.0
 
 ## Other Stuff