Provide optional dependencies for qt instead of napari

[niksirbi]

Description

What is this PR

• [x] Bug fix
• [ ] Addition of a new feature
• [ ] Other

Why is this PR needed? We were providing optional dependencies via brainglobe-utils[napari]. These included qtpy, superqt, and napari itself. I realised that the actual code for the collapsible widgets (located in the qtpy folder), doesn't actually make use of napari, so that dependency was unnecessary.

What does this PR do? We instead provide brainglobe-utils[qt], which include qtpy, superqt as before, but NOT napari. This should also simplify dependency management in packages that rely on the collapsible widgets.

References

I realised this while working on a napari widget for movement

How has this PR been tested?

Existing tests still pass (because napari was actually never even installed in the dev environment).

Is this a breaking change?

In a way, packages that depended on collapsible widgets (brainglobe-stitch and brainglobe-registration?) need to update their dependencies to brainglobe-utils[qt], and make sure to have a separate napari dependency. That's why I'm tagging @IgorTatarnikov as reviewer.

Does this PR require an update to the documentation?

The README has been updated accordingly.

Checklist:

• [ ] The code has been tested locally
• [ ] Tests have been added to cover all new functionality (unit & integration)
• [x] The documentation has been updated to reflect any changes
• [x] The code has been formatted with pre-commit

[codecov[bot]]

Codecov Report

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

Project coverage is 91.59%. Comparing base (a64cd9a) to head (52a8fdc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #84 +/- ## ======================================= Coverage 91.59% 91.59% ======================================= Files 35 35 Lines 1607 1607 ======================================= Hits 1472 1472 Misses 135 135 ``` | [Flag](https://app.codecov.io/gh/brainglobe/brainglobe-utils/pull/84/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=brainglobe) | Coverage Δ | | |---|---|---| | [numba](https://app.codecov.io/gh/brainglobe/brainglobe-utils/pull/84/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=brainglobe) | `91.53% <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=brainglobe#carryforward-flags-in-the-pull-request-comment) to find out more.

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