Draft blog post for DataFusion Comet 0.2.0 release

[Andy Grove]

Here is a draft blog post for the DataFusion Comet 0.2.0 release announcement. 
Feedback + contributions are welcome.

https://docs.google.com/document/d/1A2dq_Z570TU-ba_jwC5LbiNnIdoDt6gGdBTAYy4MJ6s/edit?usp=sharing

Thanks,

Andy.