First, this sets up appium for component testing via selenium-webdriver-at-spi. Second, it fixes some accessibility problems in the sticker picker:

• Focus styles for stickers
• Stickers can be triggered using keyboard
• Use sticker body for accessible name of sticker buttons

Type: fix

CCBUG: https://iron.lily-is.land/T185

Check the appium test passes on the pipeline. Check you can tab into stickers to receive focus styles, and you can use space button to send a sticker when focused on it.