feat: Implement Prometheus metrics exposure in SmartMetrics

- Added Prometheus gauges for CPU and memory metrics.
- Implemented HTTP server to expose metrics at /metrics endpoint.
- Created methods to enable and disable the Prometheus endpoint.
- Updated getMetrics() to set gauge values.
- Added tests for Prometheus metrics functionality.
- Updated documentation plan for Prometheus integration.

ts/smartmetrics.plugins.ts

@@ -2,8 +2,9 @@
 import * as v8 from 'v8';
 import * as os from 'os';
 import * as fs from 'fs';
+import * as http from 'http';
 
-export { v8, os, fs };
+export { v8, os, fs, http };
 
 // pushrocks scope
 import * as smartdelay from '@push.rocks/smartdelay';