Add Other Resources subpage on Digital Accessibility

For instance, adding alt-text and checking color contrast:
- Resource for testing foreground-background color contrast: https://contrast-finder.tanaguru.com/ also https://webaim.org/resources/contrastchecker/ and https://colorbrewer2.org/#type=sequential&scheme=BuGn&n=3 (last one I just learned about). There's also a Chrome WAVE extension
- Another one: https://coolors.co/contrast-checker/667faf-1f2129
- Microsoft does have built-in accessibility checkers (for when you use e.g., Word, PowerPoint, Excel)--use throughout.
- Another resource from OSU ETS: https://accessible.org/wcag-2-1-aa-guide-for-beginners-or-experts-plain-english/
- https://www.fabiocrameri.ch/colourmaps/

No file or test is named; inspect the repository's existing Digital Accessibility documentation structure first. Use the issue's resource list for the requested Other Resources subpage, then verify that the links and accessibility guidance are present and the page is reachable from the guide.

Written by the indexing model from the issue text.