Add per-test timeout option

[cloudrac3r]

Now each test can have its own timeout option, like this:

test("long test", t => {
  t.equal(longCalculation(), 42)
}, {timeout: 60000})

This is useful when most tests are quick and some are slow.

If there's no timeout option, the SUPERTAPE_TIMEOUT environment variable takes effect. This defaults to 3000ms like before.

This change is backwards compatible with previous supertape versions.

[coderaiser]

Nice! Please fix lint (npm run fix:lint)

[coderaiser]

Thanks a lot! merged as 4aeb021, landed in 📼Supertape v10.3.0 🎉