fix: allow title on button-name

[marcysutton]

This change makes it more clear that title is allowed for accessible naming of button elements and button inputs.

Closes #747
Closes #765

[iamrafan]

@marcysutton title is already being allowed as an accessible name for <button> elements. #765 is more about the fix messages conveying that only title can be used as an accessible label when button-name rule fails on <button> elements for not having any accessible label

[marcysutton]

The change in this PR explicitly adds the non-empty-title check so it will expose title as a method to fix. Here is the failureSummary with this change, you can see the new bit at the end:

"Fix all of the following:
  Element is in tab order and does not have accessible text

Fix any of the following:
  Element has a value attribute and the value attribute is empty
  Element has no value attribute or the value attribute is empty
  Element does not have inner text that is visible to screen readers
  aria-label attribute does not exist or is empty
  aria-labelledby attribute does not exist, references elements that do not exist or references elements that are empty or not visible
  Element's default semantics were not overridden with role="presentation"
  Element's default semantics were not overridden with role="none"
  Element has no title attribute or the title attribute is empty"```

[iamrafan]

sure, thanks for the clarification.