meet-default-mic per sjahu

See https://github.com/sjahu/meet-default-mic.

When using Google Meet in Firefox on macOS, my AirPods are only automatically picked as the input device if they're connected and set as the system default input device before Google Meet is opened. After they're connected, Meet won't switch to them automatically if it was opened before they were made available. Since I constantly forget to connect them in advance, I frustratingly often have to manually select them as the input device. This extension opens the settings pane after a meet.google.com page loads and forces the selection of the specified microphone, waiting until that microphone is available before closing the settings.

This is hacky and you probably shouldn't use it.