implement lettercase feature

[RED-ROSE515]

#2424

I implemented lettercase features( LowerCase, UpperCase, SentenceCase, TitleCase) to the ToolBar.

These are the screenshots.

[raineorshine]

Thank you! This is a great stat. Thanks for adding a unit test as well.

Please always reference the associated issue number in the PR description. That way GitHub will link the PR to the issue. I've added it above.

It looks like the Linter, Tests, and Puppeteer tests are all failing in the CI. Once these are all passing I can do a proper review.

I will note that useWindowOverlay has been duplicated in the ColorPicker and LetterCasePicker component. As mentioned in the issue, and following the DRY principle, we want to avoid code duplication. Code duplication doubles the amount of code to maintain and leads to subtle discrepancies over time. Instead, factor out the common code and use the appropriate level of abstraction to share common functionality.

[raineorshine]

Thank you! Looks very good. I've offered some tips below to clean up the code a bit.

There are just a couple behavioral issues I am seeing:

1. Let's prevent both the ColorPicker dropdown and the LetterCase dropdown from being open at the same time. If one is clicked, the other one should close.
2. The browser selection (i.e. text cursor) is not being preserved when it starts at the end of the thought. I'm guessing that selection.restore does not work in this case because savedSelection.node is not the same after the thought re-renders.

[raineorshine]

This project uses PandaCSS for styling. The style attribute should only be used for styles with dynamic runtime values. Otherwise you should use Panda's css function. See other components for usage, or check out https://panda-css.com/docs/concepts/writing-styles.

[raineorshine]

When you rebase on main, note the signature for isDropdownOpen has changed: 9b340a2