Allow numbers in `style:` directive

[PuruVJ]

Is your feature request related to a problem? Please describe.
In style: directive syntax, you can't pass a number. Svelte's VSCode extension errors out when you attempt something like style:z-index={someNumericalValue}, so you have to apply hacks like style:z-index={someNumericalValue + ''} to coerce it into a string, which looks really ugly.

Describe the solution you'd like
I recommend language-tools don't error out when value passed is a number, as that is a valid value for properties like z-index, width, height, block-*, top, bottom, inset, opacity, and many more, including all the CSS Variables style:--opacity={someNumber}.

This would work because we know JS coerces numbers into strings when needed, so svelte core itself doesn't need to be changed

Describe alternatives you've considered
Not do anything

[dummdidumm]

I tend to agree with this request. I doubt that many people would pass a wrong value type by accident, so the benefits outweigh the type correctness in this case. We could possibly add a list of style props that would be ok with a number but that feels like bloating the bundle size.

[PuruVJ]

Why not allow for any value? 🤔

[Tymek]

Template literal looks marginally better style:z-index={`${someNumericalValue}`}. What's the disadvantage of allowing numbers everywhere? TS will not check for example if a CSS unit is correct 3REMS 🤔

[PuruVJ]

Thank you so much for this Simon 🙇