feat(preview): custom title

[joaomendoncaa]

This is a functioning PR to close #1562.

This adds the optionality of a custom title string in the toggle_preview mapping. There's the potential to improve it with a lambda (instead of limiting to only a custom string), but as a start, it already suffices my personal needs.

1. It doesn't break anything
2. It adds an util to traverse nested tables and find a table with a specific value in it
3. It removes an hardcoded value (preview's title nui popup)
4. It fixes a personal health issue

...is that enough to sell it? 😅

I'd be happy to ear any considerations/requests for improvement, happy to help. Feel free to ask any questions.

I noticed there were tests, but if I understood correctly, it's out of scope to unit test the util.table_find_by_value I added.

Thank you for your time in advance to whoever takes a look at this PR. 🍻