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

plugins/tunnels/CONTRIBUTING.md

@@ -0,0 +1,22 @@
+# Contributing to Tunnels
+
+## 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
+
+### Host
+
+- **Enable tunnels:** set up SSH tunnels through this host
+- **Tunnels:** the type, ports, endpoint host, auto start, max retries and retry interval for each tunnel
+
+## Permissions
+
+- `tunnels.use`: start, stop and watch tunnels, and save client tunnel presets. Admins and users have it by default.