fix: merge and simplify redundant 'findSlot' func

[Marco-Pagani]

While working with this package I found that findNextSlot and findPrevSlot do exactly the same thing, with the logical operations written slightly differently. Both functions boil down to a single condition:

for (let i = 0; i < children.length; i++) {
  const rect = children[i].getBoundingClientRect()

  if ( x <= rect.right) return children[i]
  else continue
}

I combined these functions into one new function, and I also rewrote it using Array.find instead of a for loop to make it more concise.

This doesn't change any behavior of the package, just makes the code cleaner and easier to maintain. I hope this helps!

[netlify]

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[Marco-Pagani]

I'll try to take a look at the test failures sometime soon, I didn't see that happening on my local