Add tested-with field in cabal file.

Author: pranaysashank

fusion-plugin-types.cabal

@@ -8,6 +8,8 @@ homepage: https://github.com/composewell/fusion-plugin-types
 bug-reports: https://github.com/composewell/fusion-plugin-types/issues
 license: BSD-3-Clause
 license-file: LICENSE
+tested-with: GHC==8.6.5
+ , GHC==8.8.1
 author: Pranay Sashank
 maintainer: pranaysashank@composewell.com
 copyright: (c) 2020 Composewell Technologies