Call for review: Error message, improve on examples

Hey folks,
This pull request tweaks three examples in the "Error message describes
invalid form field value" rule. These tweaks are designed to help make the
rule a little easier to understand. If you have any comments, please leave
a review by May 6th:

https://github.com/act-rules/act-rules.github.io/pull/1825

Kind regards

-- 
*Wilco Fiers*
Axe-core & Axe-linter product owner - WCAG 3 Project Manager - Facilitator
ACT Task Force