Enable all tested-with GHC versions

Author: Gaël Deest

.github/workflows/main.yml

@@ -89,7 +89,7 @@ jobs:
     strategy:
       matrix:
         stack: ["2.3.1"]
-        ghc: ["8.8.4"]
+        ghc: ["8.0.2", "8.2.2", "8.4.4", "8.6.5", "8.8.4", "8.10.2"]
 
     steps:
     - uses: actions/checkout@v2