[ecashaddrjs] Add unit tests and support autodeploy

Summary:
Add unit tests to confirm type checking works for this cashaddr validation function.

Since ecashaddrjs does not have autodeploy, add it here. We wouldn't normally do a version bump for this kind of diff, but it's a good excuse to get the autodeploy working.

Test Plan: npm test

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15023