Add Chromium as a supported browser for VoiceOver (MacOS)

[aleventhal]

Chromium covers both Edge and Chrome. It could be written as Edge+Chrome or something like that, since most authors may not know that. But, the testing only needs to be done once, since Edge and Chrome have identical accessibility on Mac.

Side note: Chrome's and Edge's accessibility implementation are the same except for UI Automation support on Windows. However, those are also going to be identical in a year, when Chrome goes to 100% direct support and stops using the bridge. After that, it technically will not be necessary to have separate data or separate testing for them. And really, that's already true for anything other than Narrator, since no other screen reader uses UI Automation.