Add default box shadow reset

[RobinMalfait]

This PR adds a reset for the shadow to each input element, this is necessary because we are trying to get rid of the universal selector.

See: tailwindlabs/tailwindcss#5517
Fixes: tailwindlabs/tailwindcss#5042

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[adamwathan]

We'll need to add this to the other elements that use shadows for focus rings too, like checkboxes/radios/maybe others 👍🏻

[RobinMalfait]

@adamwathan Good catch! Updated the others as well, only added it for the "base" elements (so not for the ones with :checked or other pseudo's)

[RobinMalfait]

Before	After

Notice the incorrect shadow when the input has focus.

[adamwathan]

Is this one needed? I can't think for sure but maybe it's not since we don't use box-shadow for any focus styles on file inputs?

[RobinMalfait]

Aha, yeah I added it because I wanted to make sure that I got all the base cases, but we are indeed not adding any focus styles for this one.
However if we eventually do, probably not though, then we can't forget to add these back.

[adamwathan]

Looking good man thanks! I think we can simplify the box shadow calls to this now:

- 'box-shadow': `var(--tw-ring-offset-shadow), var(--tw-ring-shadow), var(--tw-shadow, 0 0 #0000)`,
+ 'box-shadow': `var(--tw-ring-offset-shadow), var(--tw-ring-shadow), var(--tw-shadow)`,

...since --tw-shadow will always be set. Super minor but code does nothing and makes the CSS bigger, so better to delete than have to wonder why it's there in the future when the details of this are out of mind.