Add missing input definition for enable_cache feature flag asdf-vm#235

Author: flosell

install/action.yml

@@ -27,6 +27,10 @@ inputs:
     description: setup env without installing asdf
     required: false
     default: false
+  enable_cache:
+    description: cache asdf plugins and installs
+    required: false
+    default: false
   github_token:
     description: Token used to avoid rate limit when asdf calls the GitHub API
     required: false