fix ARIA role of transcript when connection is pending

[beyackle2]

Fixes #4393

Changelog Entry

Description

The ARIA role of the transcript was incorrectly set when the connection was pending; this is what aria-busy is meant for, so we needed to incorporate awareness of the connection status into the transcript.

Specific Changes

• Added "isWaiting" to BasicTranscript to see if the user is waiting for a connection
• Wired this prop through to both places that needed it

• [ ] I have added tests and executed them locally
• [x] I have updated CHANGELOG.md

Review Checklist

This section is for contributors to review your work.

• [ ] Accessibility reviewed (tab order, content readability, alt text, color contrast)
• [ ] Tests reviewed (coverage, legitimacy)

[ghost]

All CLA requirements met.

[compulim]

Looks like aria-busy="true" won't help with the accessibility issue. Few things we could try:

• Change role to something else until the first message come
• Inject an invisible "the chat history is empty" in the transcript before the first message

[compulim]

@beyackle2 Few things I changed:

• Now, it renders <section role="feed"> if there are any contents
• For tests, I am adding this DOM integrity test to verifyDOMIntegrity.js, which is a tiny version of axe-core
  • Ultimately, we should use axe-core and replace verifyDOMIntegrity.js (outlined in #3716)
  • However, axe-core is using a non-MIT license so we need to do something extra before using it
  • Thus, we have the tiny verifyDOMIntegrity.js as a stopgap for now

Please let me know if it looks good to you.