[ecash-agora] Catch up changelog for next published version

Summary:
We have not published ecash-agora (officially) yet, though there is a 0.1.1 rc version on npm.

Lots of work has been going on in the meantime.

It can be useful to have this sort of reference available for an npm user who may not be familiar with searching phab.

Test Plan: Check readme, won't land this until we are going to publish, so pending review of D16944

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D16973