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

plugins/session-recording/CONTRIBUTING.md

@@ -0,0 +1,25 @@
+# Contributing to Session Recording
+
+## 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
+
+- **Retention (days):** remove recordings older than this. Checked at startup and once a day
+
+### Host
+
+- **Enable session recording:** record sessions on this host
+
+## Permissions
+
+- `session-recording.view`: view and play back your own session recordings. Admins and users have it by default.