feat: css unit handling for fly transition

[simondehaut]

It would be great to be able to give CSS unit parameter to transition fly function.

'fly' is the best candidate. It defines an absolute/arbitrary transformation while the others define rather a transformation relative to an existing div's style.

Units are quiet often left behind in a lot of js library, 'px' is not the only one :)

use: <div transition:fly={{ y: 1, unit: 'em' }}></div>

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• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with npm test and lint the project with npm run lint

[techniq]

This is useful to perform 100% transitions (ex. hiding a drawer).

Instead of passing a unit option, x and y could support passing a string (ex. 100%, 1em, etc) to include the units, and then parsed it via some regex (this is the approach of my drawer repl). This also allows x and y to define different units.

[whatwhywhenandwho]

This seems to be ok. Can someone restart the checks, so we can get this out? 😬

[whatwhywhenandwho]

In all seriousness, I can't think of another way to close this, than to just keep on pinging, and perhaps someone seeing it in their inbox. So, again, this seems to be ok. Can someone restart the checks, so we can get this out? 🙂

[dummdidumm]

Closing in favor of #7623 - thank you!