update readme for prometheus

prometheus/README.md

@@ -0,0 +1,10 @@
+# prometheus
+Categraf simply wrapped prometheus agent mode fuction, which means you can scrape metrics like prometheus do and get full support with prometheus plugins, such as service discovery and relabel.
+
+For more details, see the official docs:
+- https://github.com/prometheus/prometheus/tree/main/documentation/examples
+
+## Configuration
+
+An [example](../conf/in_cluster_scrape.yaml) to scrape kube-apiserver and core-dns metrics .
+more examples click [here](https://github.com/prometheus/prometheus/tree/main/documentation/examples)