Add job runner timeout option

[markuswustenberg]

Otherwise, the underlying queue could have a much smaller timeout, and the runner wouldn't work properly.

Also:

• Remove the done channel, we can just use jobCtx directly.
• Some more doc comments.
• Add logging before job run.
• Add a test for the extension.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 89.30%. Comparing base (95eb0b8) to head (3bc7f69).

:exclamation: Current head 3bc7f69 differs from pull request most recent head c0f1701. Consider uploading reports for the commit c0f1701 to get more accurate results

Files	Patch %	Lines
jobs/runner.go	83.33%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #40 +/- ## ========================================== - Coverage 89.47% 89.30% -0.17% ========================================== Files 3 3 Lines 342 346 +4 ========================================== + Hits 306 309 +3 - Misses 27 28 +1 Partials 9 9 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.