chore: rework plugin readmes, json changelogs and standalone repo setup

plugins/workspaces/CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# Contributing to Workspaces
+
+## Development
+
+```bash
+npm run build      # build into dist/
+npm run test       # run this plugin's tests
+npm run typecheck  # type-check this plugin
+npm run validate   # check manifest.json
+npm run format     # format the code with Prettier
+```
+
+## Permissions
+
+- `workspaces.use`: save, apply and manage workspaces. Admins and users have it by default.