Add gitignore rule for workspace extensions working/scratch folder

Checkpoint before drafting the Workspace Extensions documentation section.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: dzucker-tab

.gitignore

@@ -8,6 +8,9 @@ website/build
 website/.docusaurus
 website/.cache-loader
 
+# Working/scratch files for in-progress docs
+website/docs/workspaceext/working/
+
 # Misc
 **/.DS_Store
 .env.local