Final call: Improve examples for button-accessible-name

Hey folks,

Another final call, this time an update to the Button has accessible name
rule. We are reworking some of the example descriptions, and I've cleaned
up some of the examples as well.

This final call ends on January 21st. If you have any comments, please
leave a review on the pull request before that time:
https://github.com/act-rules/act-rules.github.io/pull/1028/

-- 
*Wilco Fiers*
Axe for Web product owner - Co-facilitator WCAG-ACT - Chair ACT-R