Add git source to subosito/flutter-action@v2 (#58)

Author: krzema12

typings/subosito/flutter-action/v2/action-types.yml

@@ -29,6 +29,8 @@ inputs:
     type: string
   pub-cache-path:
     type: string
+  git-source:
+    type: string
 
 outputs:
   CACHE-PATH:
@@ -45,3 +47,5 @@ outputs:
     type: string
   PUB-CACHE-PATH:
     type: string
+  GIT_SOURCE:
+    type: string