Supports only posts with plain photos, and loses all message
formatting, but it's getting there.
Change-Id: I9e4afcf3072d1e0724521ccbdc1338fe4f8d5ebe
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5466
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
