Add JavaDoc.io badge (#15)

Author: swtwsk

README.md

@@ -1,6 +1,7 @@
 # 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)
+[![javadoc](https://javadoc.io/badge2/com.getindata/flink-http-connector/javadoc.svg)](https://javadoc.io/doc/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.
 
@@ -24,6 +25,10 @@ Currently, HTTP TableLookup connector supports only Lookup Joins [1] and expects
 
 In order to use the `flink-http-connector` the following dependencies are required for both projects using a build automation tool (such as Maven or SBT) and SQL Client with SQL JAR bundles. For build automation tool reference, look into Maven Central: [https://mvnrepository.com/artifact/com.getindata/flink-http-connector](https://mvnrepository.com/artifact/com.getindata/flink-http-connector).
 
+## Documentation
+
+You can read the official JavaDoc documentation of the latest release at [https://javadoc.io/doc/com.getindata/flink-http-connector](https://javadoc.io/doc/com.getindata/flink-http-connector).
+
 ## Usage
 
 ### HTTP TableLookup Source