fix(useScrollLock): initialOverflow is not working

[BJ0815]

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Description

This PR makes a change to ensure that the initial overflow value is correctly saved.

Additionally, a test case has been added to cover this change.

Additional context

[ChristophJeworutzki]

Thank you for this PR!

I've come across a little hiccup since this update.

It seems that in certain scenarios, overflow: hidden persists or is reapplied after setting scrollLock to false

I have a feeling this might be tied to a race condition, where overflow: hidden is being incorrectly set as the "initial state."

Just wanted to bring it to your attention!

Thanks again for all your work on this!