DOC: release notes for 1.3.0 Styler
Added a note to the enhancements section detailing some different upgrades to `Styler` for 1.3.0

If this is not standard or unnecessary just close this PR - I'm only including it in case it is helpful (it is not for self-publication), so I am completely indifferent!

Hopefully there will be one or two more items to add before the end of May.

can you merge master and ping on green @jreback pinging green now