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

plugins/host-metrics/CONTRIBUTING.md

@@ -0,0 +1,34 @@
+# Contributing to Host Metrics
+
+## 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
+
+- **Metrics interval (seconds):** how often a host is checked while someone views it
+- **History retention (days):** how long history is kept for the charts
+- **Metrics on for new hosts:** whether new hosts start with metrics turned on
+
+### User
+
+- **Temperature unit:** Celsius or Fahrenheit
+
+### Host
+
+- **Collect metrics:** turn metrics on for this host
+- **Metrics interval (seconds):** use a different interval for this host
+- **Excluded mounts:** mount points or filesystem types to hide
+- **Monitored paths:** extra paths to watch that are not separate mounts
+
+## Permissions
+
+- `host-metrics.use`: view metrics and use the manager cards. Admins and users have it by default.