CI: Add ghc-9.6.1 to build matrix

Author: erikd

.github/workflows/haskell.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ghc: ["8.10.7", "9.2.7", "9.4.4"]
+        ghc: ["8.10.7", "9.2.7", "9.4.4", "9.6.1"]
         os: [ubuntu-latest, macos-latest, windows-latest]
 
     env: