Add visual highlighting for web math navigation

[RyanMcCleary]

Link to issue number:

Partially addresses #19191. To fully resolve that issue, we would want to implement highlighting for Microsoft Word as well.

Summary of the issue:

When navigating math, there is currently no visual highlighting showing the focused subpart. Visual highlighting is very useful for low-vision users and can make it easier to use speech and magnification together while reading math.

Description of user facing changes:

Adds a new highlighter for math, which highlights the currently focused subpart of the math being navigated in orange. I also considered making this part of the browse mode highlighter, and I'm still definitely open to suggestions on this front. I decided to leave it as a separate highlighter because math navigation is distinct from browse mode, even though it's usually activated from browse mode. I chose orange as the highlighting color because it's easier for me to see on a white background than yellow.

Description of developer facing changes:

Adds a new math highlight context to the vision framework and wires MathCAT navigation updates to it. The MathCATInteraction class now takes a source object as a constructor parameter (the source object is the root of the MathML being interacted with). A new file source\mathPres\MathCAT\navNodeMapping.py was also added. This file contains functions that are used to map from MathCAT's current navigation node to the corresponding IA2 object.

Description of development approach:

Testing strategy:

Known issues with pull request:

Code Review Checklist:

• Documentation:
  • Change log entry
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• API is compatible with existing add-ons.
• Security precautions taken.