Improve doc with more examples for sinks and sources.
Improve doc with more examples for sinks and sources.

dilini-muthumala/siddhi,tishan89/siddhi,dilini-muthumala/siddhi,grainier/siddhi,gokul/siddhi,tishan89/siddhi,wso2/siddhi,ramindu90/siddhi,gokul/siddhi,mohanvive/siddhi,grainier/siddhi,wso2/siddhi,suhothayan/siddhi,ramindu90/siddhi,suhothayan/siddhi,mohanvive/siddhi