Add 'cabal: true' option to enable caching

  * Caches `output.cabal-store` and `./dist-newstyle`

  * Currently `hashFiles` is not exposed in the actions/cache API,
    hence the use of `folder-hash.hashElements`

Author: omelkonian

setup/.eslintignore

@@ -3,3 +3,4 @@ lib/
 .out/
 __tests__/
 node_modules/
+*.json

setup/action.yml

@@ -23,6 +23,9 @@ inputs:
   stack-setup-ghc:
     required: false
     description: 'If specified, enable-stack must be set. Will run stack setup to install the specified GHC'
+  cache:
+    required: false
+    description: 'If specified, automatically caches the cabal-related folders.'
 outputs:
   ghc-path:
     description: 'The path of the ghc executable _directory_'

setup/dist/action.yml

@@ -23,6 +23,9 @@ inputs:
   stack-setup-ghc:
     required: false
     description: 'If specified, enable-stack must be set. Will run stack setup to install the specified GHC'
+  cache:
+    required: false
+    description: 'If specified, automatically caches the cabal-related folders.'
 outputs:
   ghc-path:
     description: 'The path of the ghc executable _directory_'