Accessibility Fixes

[pancakereport]

Follow up to #6

Issues include

• Violation of "image-alt"
• Violation of "color-contrast"
• Violation of "aria-allowed-attr"
• Violation of "scrollable-region-focusable"

Alt Text

Alt text is kind of a mess with quarto; highly configurable but reasonable defaults aren't applied. Documentation of the various options here. Because a figure's caption is considered separately from alt text, I've decided to leave the captions as they were originally written and insert empty alt text as suggested by Web AIM after I made the alt text the same as the figure caption: "Change either the alternative text or the adjacent text to eliminate the redundancy. In most cases, you can give the image empty/null alternative text (alt="") because the content of the image is already provided in context through text."

Color Contrast

Color contrast violations appear when code cells intentionally output errors for instructional purposes. I added custom CSS to use high contrast colors. I also removed a code element from a link; "Why? Find out the answer in the official Python documentation on pop!" became: "Why? Find out the answer in the official Python documentation on pop!"

Aria Allowed Attributes

This violation has to do with callout-note's like at the bottom of 16-measurements/iteration-ii.html. I added a script that will inject role="button" to fix this.

Scrollable Region Focusable

This violation appears for scrollable regions like wide blocks of code. I added a script that injects tabindex=0 so they are able to be accessed by keyboard users.