Extend back to 8.4.4 support.

Author: tmcgilchrist

.github/workflows/haskell.yml

@@ -14,7 +14,7 @@ jobs:
       matrix:
         os:    [macos-latest, ubuntu-latest]
         cabal: ["3.8"]
-        ghc:   ["8.10.7", "9.0.2", "9.2.6", "9.4.4"]
+        ghc:   ["8.4.4", "8.6.5", "8.8.4", "8.10.7", "9.0.2", "9.2.6", "9.4.4"]
 
     runs-on: ${{ matrix.os }}