Paste the info from the blog post into the project docs

[tzach]

The blog post gives a lot good context and info we can include in the project itself https://docs.google.com/document/d/1x_CpO3yIEX8dxyjAj1pk5XLedPjK9Xozi6ZALX1_z0U/edit?ts=5ffeff01#heading=h.1dom5c5t1xrn

[avelanarius]

The main usage of library was already described in this subpage: https://github.com/scylladb/scylla-cdc-java/tree/master/scylla-cdc-printer. The text from blogpost actually originated from this subpage. It is linked from the main README ("Next steps").

As there were certain changes made when publishing the blogpost, I integrated them back into that subpage. Also copied the "Why Use a Library?" section from the blogpost into the main README.

[haaawk]

so can this issue be closed then? @tzach @avelanarius ?