Bug 1095868 - make progress dots clickable

Bug 1095868 - Sequential form: Provide clearer way to go back to previous step
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Only preceding dots of the current active one should be clickable
Not sure if this is better, but maybe make this function: https://github.com/mmmavis/bsd-forms-and-wrappers/blob/bug-1095868-clickable-progress-dots/0-donation-forms/EOY-donation-form-sequential/below-form-content.html#L289-L300

A separate function that accepts a page index as a single param.

Then the next button can call the function and pass in `current + 1` and your buttons can call it and pass in their page?