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

plugins/telemetry/CONTRIBUTING.md

@@ -0,0 +1,26 @@
+# Contributing to Usage Statistics
+
+## 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
+```
+
+## Settings
+
+### Admin
+
+- **Share anonymous usage statistics:** turn the daily report on or off
+- **Include platform info, Include feature usage and Include installed features:** choose what the report includes
+
+### User
+
+- **Include my feature usage:** count which kinds of tabs you open in the report
+
+## Permissions
+
+- `telemetry.manage`: see what is sent, send it now and reset the instance ID. Only admins have it by default.