Adding qulacs to extra

[scarrazza]

Closes #1409.

Checklist:

• [ ] Reviewers confirm new code works as expected.
• [ ] Tests are passing.
• [x] Coverage does not decrease.
• [x] Documentation is updated.

[alecandido]

Apparently, tests are randomly failing (they were all because of numerical values). I'm rerunning them, but that's an issue on its own. https://github.com/qiboteam/qibo/actions/runs/10226346562/attempts/1?pr=1410

[scarrazza]

I think this is due to the torch version update. If I don't update the lock file, tests are passing: https://github.com/qiboteam/qibo/actions/runs/10226488301. I will probably revert the torch update.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.94%. Comparing base (64d78bc) to head (9f1f3dd). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1410 +/- ## ======================================= Coverage 99.94% 99.94% ======================================= Files 78 78 Lines 11222 11222 ======================================= Hits 11216 11216 Misses 6 6 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibo/pull/1410/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibo/pull/1410/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `99.94% <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=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

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