action: fix branding

Also ensure that action is validated against the GitHub Action schema.

Signed-off-by: Paul Jolly <[email protected]>

Author: myitcv

action.cue

@@ -1,16 +1,20 @@
 package action
 
-action: {
+import "json.schemastore.org/github"
+
+action: github.#Action & {
 	name:        "Setup CUE environment"
-	icon:        "terminal"
 	description: "Setup a Go environment and add it to the PATH."
 	inputs: version: {
 		description: #"The CUE version to setup. Must be a valid semantic version string like "v0.4.0" or "latest""#
 		required:    true
 		default:     "latest"
 	}
 	outputs: "cue-path": description: "Path to the cached CUE binary"
-	branding: color: "blue"
+	branding: {
+		icon:  "terminal"
+		color: "blue"
+	}
 	runs: {
 		using: "node12"
 		main:  "dist/index.js"