Add chartability points to our accessibility checking guidance

**Is your feature request related to a problem? Please describe.**
Don’t need to do everything from here, but should review and add any we feel we should be checking for in dashboards:

[Workbook](https://chartability.github.io/POUR-CAF/)

**Describe the solution you'd like**
Review and add anything we feel we should be checking for in dashboards:

[Workbook](https://chartability.github.io/POUR-CAF/)

Start by reviewing the linked Chartability POUR-CAF workbook alongside the existing accessibility-checking guidance. Done means the relevant dashboard checks selected by the project are added to the guidance; the issue does not name a file or test.

Written by the indexing model from the issue text.