Assets: Add README.md about syncing

.github/workflows/sync-assets-to-plugin-repo.yml

@@ -5,7 +5,8 @@ on:
         branches:
             - trunk
         paths:
-            - assets/**
+            - 'assets/**'
+            - '!assets/README.md'
 
 jobs:
     sync-assets:
@@ -35,7 +36,9 @@ jobs:
                   path: git
 
             - name: Copy files from git checkout to svn working copy
-              run: cp -R git/assets/* assets
+              run: |
+                  cp -R git/assets/* assets
+                  rm assets/README.md
 
             - name: Commit the updated assets
               working-directory: ./assets

assets/README.md

@@ -0,0 +1,5 @@
+## Gutenberg Plugin Assets
+
+The contents of this directory are synced to the [`assets/` directory of the Gutenberg plugin](https://plugins.trac.wordpress.org/browser/gutenberg/assets) in the WordPress.org plugin repository. This is done by a [GitHub Actions workflow](https://github.com/WordPress/gutenberg/actions/workflows/sync-assets-to-plugin-repo.yml) that is triggered whenever a file in this directory is changed (with the exception of this README, which is excluded from the sync).
+
+Since that workflow requires access to WP.org plugin repository credentials, it needs to be approved manually by a member of the Gutenberg Core team. If you don't have the necessary permissions, please ask someone in #core-editor.