Migrate to latest yarn

[fedemp]

Since the project chose to use yarn and also add yarn.lock to version control, I consider it a best practice to make clear which package manager the use. Since official yarn docs suggest using the stable/berry version, I've set the packageManager option as so, and upgraded yarn.lock.

[tony]

@fedemp Sorry for the delay

This needs a rebase against the latest release at https://github.com/isaul32/ckeditor5-math/releases/tag/v41.2.0 (so we catch the minor version bump at 41.2.0).

[tony]

@fedemp If you are able to take a look at this and #127, I can take a look on the weekends

[tony]

@fedemp This needs the yarn.lock file updated. (or I could do it on your behalf with your permission)

[tony]

@fedemp In a normal JS/TS package, I would accept this as-is (I use berry on my own projects). I think we should focus on #99 first.

My concern: As CKEditor5 isn't using yarn berry yet, it's unknown if this could cause unexpected friction due to:

• ckeditor5's upcoming build changes: https://github.com/ckeditor/ckeditor5/issues/15502
• https://www.npmjs.com/package/@ckeditor/ckeditor5-package-tools
• downstream integrators of any kind

I think since this is a CKEditor5 plugin, the more in line we are with https://github.com/ckeditor/ckeditor5, the less chance we'll hit conflicts when maintaining the package.

[tony]

@fedemp

As of CKEditor5 v41.4.2 - yarn hasn't upgraded to berry (yet).

My thinking: When CKEditor5 moves over, I believe this should be rebased and go in (unless there is a good case otherwise)