ci: add stale theme pull request closer action push (#2067)

This commit adds the `stale-theme-pr-closer` closer action. This action
is used to close theme pull requests with an `invalid` label that has
been stale for a given number of `STALE_DAYS`.

.github/workflows/generate-theme-doc.yml

@@ -1,5 +1,4 @@
 name: Generate Theme Readme
-
 on:
   push:
     branches:
@@ -8,8 +7,9 @@ on:
       - "themes/index.js"
 
 jobs:
-  build:
+  generateThemeDoc:
     runs-on: ubuntu-latest
+    name: Generate theme doc
     strategy:
       matrix:
         node-version: [16.x]