Various accessibility fixes.

[ndarilek]

• Add aria-label to Icon
• Set tabIndex, role and aria-label on Button and IconButton
• Set role and tabIndex on Link
• Label bunches of unlabeled icon-only buttons.
• Make login screen keyboard-navigable.
• Make app logo keyboard-accessible.
• Add alt attribute to SmartImage and set on cover images
• Add navigation role to sidebar.

Marking as draft for now because I can't seem to get string values in place of their keys in en.json. Is there some i18n step not included in npm start or did I get something wrong?

Thanks.

[ndarilek]

I think this one's ready, barring the issue of all strings appearing as their key rather than their value (I.e. "region.game" instead of "Game", which I asked about but couldn't get help with here, on Discord, or anywhere I looked in the docs.)

I'm a blind screen reader user and am about to release my third game on Itch. The app was already fairly usable, but these changes really make it pop, and I'd love to be able to recommend an even more accessible Itch app as the way to buy the game and keep it updated. Hoping to do more app work in the future--Steam is an accessibility dumpster fire with no signs of getting better, and while Itch can't compete in terms of some of Steam's addon platform services, I'd like to make it a no-brainer to recommend Itch for accessible game distribution.

Thanks!