ci: Automatically publish docs for new releases

[godlygeek]

An update of #223, rebased and PR'd from a branch instead of a fork so that it can (hopefully) request write permissions for the job that needs to publish the docs...

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.10% :tada:

Comparison is base (214debf) 91.55% compared to head (a428342) 91.66%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #436 +/- ## ========================================== + Coverage 91.55% 91.66% +0.10% ========================================== Files 90 90 Lines 10532 10532 Branches 1450 1450 ========================================== + Hits 9643 9654 +11 + Misses 886 875 -11 Partials 3 3 ``` | Flag | Coverage Δ | | |---|---|---| | cpp | `85.01% <ø> (+0.30%)` | :arrow_up: | | python_and_cython | `95.18% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bloomberg#carryforward-flags-in-the-pull-request-comment) to find out more. [see 4 files with indirect coverage changes](https://app.codecov.io/gh/bloomberg/memray/pull/436/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bloomberg)

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

[godlygeek]

The new job has

    if: github.event_name == 'release' && github.event.action == 'published'

so that it only runs for new releases, but I iterated on this without that guard to confirm that it works, and the docs currently up on https://bloomberg.github.io/memray/ were published by this job. Had to prove it works somehow, and it was a perfect time to do this since we just had a release and hadn't yet updated the docs 😄

[pablogsal]

Wonderful!