[Tests] migrate tests to Github Actions

[ljharb]

Per ljharb/object.assign#81

travis-ci's new pricing plan, and its defaults, have caused all my ljharb repos to have zero CI whatsoever until December. @travis-ci Support is MIA, so I unfortunately can't rely on it as a service anymore.

[paulmillr]

Allow all actions is set

[ljharb]

I'm very confused why the PR isn't triggering an actions run :-/ it's running on my fork: https://github.com/ljharb/es6-shim/runs/2470213815

[ljharb]

@paulmillr is there an "approve and run" button showing for you on the PR status box?

[paulmillr]

@ljharb I think it will only show after the merge

[ljharb]

That has not been my experience - pull_request_target workflows behave like that, but most of these are pull_request, and should work immediately.

You can see all the hundreds of PRs I linked to ljharb/object.assign#81 running on the first PR.

[paulmillr]

perhaps it depends on repo owner, which is different in your repos. let's try merging it, we can always revert

[ljharb]

I'd prefer to hold off; I'm pinging github folks about it: https://git.luolix.topmunity/t/pr-adding-actions-not-running-jobs/177497

I'll land the PR once they confirm it's a bug, or working as intended, but they might need the PR left open to debug it.

[ljharb]

Figured it out; I had to land at least one action in the default branch first to "enable" actions (which seems like a clear bug).

I'll land this once the tests pass.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (master@ad15fce). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #469   +/-   ##
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  Coverage          ?   86.05%           
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  Files             ?        2           
  Lines             ?     2352           
  Branches          ?      607           
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  Hits              ?     2024           
  Misses            ?      328           
  Partials          ?        0           

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