Update table in README regarding supported compiler versions

Author: awvwgk

README.md

@@ -87,8 +87,8 @@ The following combinations are tested on the default branch of stdlib:
 
 Name | Version | Platform | Architecture
 --- | --- | --- | ---
-GCC Fortran | 7, 8, 9, 10 | Ubuntu 20.04 | x86_64
-GCC Fortran | 7, 8, 9, 10 | MacOS Catalina 10.15 | x86_64
+GCC Fortran | 7, 8, 9, 10, 11 | Ubuntu 20.04 | x86_64
+GCC Fortran | 7, 8, 9, 10, 11 | MacOS Catalina 10.15 | x86_64
 GCC Fortran | 8 | Windows Server 2019 | x86_64
 GCC Fortran (MSYS) | 10 | Windows Server 2019 | x86_64
 GCC Fortran (MinGW) | 10 | Windows Server 2019 | x86_64, i686