[herald] Fix the headers, lint the package
Summary: The headers are enforced with a single year which is absurd. Update and lint all the files.
Test Plan:
arc lint -- apps/ecash-herald/**/*.js
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Subscribers: PiRK
Differential Revision: https://reviews.bitcoinabc.org/D16862