ci: add codecov.io coverage for mocha

[thiagowfx]

Closes: #17

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@85e2add). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head 7d89cb8 differs from pull request most recent head da943f1. Consider uploading reports for the commit da943f1 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #918   +/-   ##
=======================================
  Coverage        ?   51.90%           
=======================================
  Files           ?       23           
  Lines           ?      763           
  Branches        ?      150           
=======================================
  Hits            ?      396           
  Misses          ?      341           
  Partials        ?       26           

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[thiagowfx]

Sample report: https://app.codecov.io/github/GoogleChromeLabs/chromium-bidi/commit/7d89cb85ef5f3dcc2d9d4ae9aec2ffc1759c344a

[thiagowfx]

It's a bit hard to see the effects of this change in a PR. I'll merge it to better test it. Can always revert if needed.

[thiagowfx]

I think I'll disable comments like this: #920 (comment)

ref. https://docs.codecov.com/docs/pull-request-comments#disable-comment

They seem too noisy

For our purposes, the badge in the README and the codecov.io dashboard seem enough