[eCash webdev libraries p2] Rename to ecashjs-lib
Summary:
T2782
Depends on D12769
Rename bitcoincashjs-lib to ecashjs-lib. Update package.json and CHANGELOG.md accordingly.
Test Plan: Sanity check changes to package.json and CHANGELOG.md. Confirm other changes are related to name change of parent directory.
Reviewers: #bitcoin_abc, emack
Reviewed By: #bitcoin_abc, emack
Differential Revision: https://reviews.bitcoinabc.org/D12837