docs: add note on checkbox.md about needed input:hidden

[manicar2093]

Close #1170

Documentation was not clear about using an input:hidden to make checkbox component work. This PR adds a note in page to do more clear this step

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[huntabyte]

Thank you!

[manicar2093]

Cool, @huntabyte! I just fix that conflict to merge it!

[huntabyte]

can you resubmit this on a branch other than main so I can merge/push changes? Or if you could merge main into this to resolve the conflicts that'd be great!