Prepare 2.14 changelog

[joshmoore]

Sharding, and ensuring, and pydata themes, oh my .... 🦁 🐯 🐻

Open to suggestions to have this go out as an rc first, otherwise 🚀

[joshmoore]

I'm failing to get the two-level bullets to render correctly, but the single level bullets look much nicer!

[joshmoore]

Issue raised during community meeting:

• get v3 and transforms docs published (cc: @jstriebel)
• small changes to Allow reading utf-8 encoded json files  #1312

and then roll it out!

[joshmoore]

#1312 has been included and is updated in the release notes.

API additions are in #1345 but holding off on those for further review.

🚀