Merge pull request #10 from getindata/ReadmeUpdate

ReadmeUpdate - add Maven link to readme, add Maven Central badge

Author: kristoffSC

README.md

@@ -1,6 +1,12 @@
 # flink-http-connector
+
+[![Maven Central](https://img.shields.io/maven-central/v/com.getindata/flink-http-connector)](https://mvnrepository.com/artifact/com.getindata/flink-http-connector)
+
 The HTTP TableLookup connector that allows for pulling data from external system via HTTP GET method and HTTP Sink that allows for sending data to external system via HTTP requests.
 
+**Note**: The `main` branch may be in an *unstable or even broken state* during development.
+Please use [releases](https://github.com/getindata/flink-http-connector/releases) instead of the `main` branch in order to get a stable set of binaries.
+
 #### HTTP TableLookup Source
 The goal for HTTP TableLookup connector was to use it in Flink SQL statement as a standard table that can be later joined with other stream using pure SQL Flink.