chore: add prometheus back with API and SDK pinned at 0.23

Author: TommyCpp

opentelemetry-prometheus/src/lib.rs

@@ -1,6 +1,6 @@
 //! An OpenTelemetry exporter for [Prometheus] metrics.
-//! 
-//! <div class="warning"> The development of prometheus exporter has halt until the Opentelemetry metrics API and SDK reaches 1.0. Current 
+//!
+//! <div class="warning"> The development of prometheus exporter has halt until the Opentelemetry metrics API and SDK reaches 1.0. Current
 //! implementation is based on Opentelemetry API and SDK 0.23.</div>
 //!
 //! [Prometheus]: https://prometheus.io