bug/minor: WCAG: fix 'Missing form label'

[eltouma]

This change builds on the fix introduced by @xJuvi in #934

TomSelect renders a focusable <input> inside .ts-control to implement the placeholder/search UI:

const placeholder = getDom('<input class="items-placeholder" tabindex="-1" />') as HTMLInputElement;
placeholder.placeholder = self.settings.placeholder || '';
self.control.append(placeholder);

Even when the source is correctly labelled, its aria-label is not always propagated to that generated input. As a result, accessibility checkers may report a “Missing form label” warning. This patch ensures the generated input inherits the original aria-label, keeping the enhanced control accessible while preserving existing behavior.

[xJuvi]

It would also be great if you could add a description to your pull request. This should include what you changed and why.
Thank you very much for your contribution!

[NicolasCARPi]

@xJuvi new commit has been pushed with code in the right place, we'd appreciate your review :)

[xJuvi]

Looks good. Thanks for the changes.