Screenshot optimization: improve Screenshottable

[data-sync-user]

I just looked at the Screenshottable, and what we should likely do is:

• render at 1x (currently we're tying quality to render scale, which is probs not great)
• control compression (we should use JPG - maybe even HEIC? I think that's ios 11+, right? - instead of render scale; JPG even at 0.7 quality is gonna be small; HEIC, is more quality preserving but even smaller footprint while having higher legibility)
• even better improvement... maybe we store stuff as Data instead of a RawImage . Not sure how much of an improvement this'll be.

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