Headless mode for ATs and/or a concept of sessions

[zcorpan]

From the ARIA-AT automation meeting on March 14, 2022: w3c/aria-at-automation#17 (minutes) and March 28, 2022 (minutes)

• Browsers already have a headless mode. But may not be compatible with screen readers.
• Would it be possible to make a headless mode for screen readers? Meaning to not output to the system TTS engine, but still available in the API.
  • Use case: run tests locally without turning off the user's screen reader or change the TTS voice setting.
• Would it be possible to have a concept of sessions for screen readers where simulated input is directed to a particular session?

Related: w3c/aria-at#11

cc @cookiecrook @mcking65 @s3ththompson @mzgoddard