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

plugins/tailscale/CONTRIBUTING.md

@@ -0,0 +1,23 @@
+# Contributing to Tailscale
+
+## 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
+
+- **API key:** a Tailscale or Headscale API key for your tailnet
+- **API base URL:** leave empty for Tailscale, or point it at a Headscale instance
+- **Device list:** check that the key works and see how many devices are reachable
+
+## Permissions
+
+- `tailscale.devices.view`: see the devices on the tailnet. Only admins have it by default.