Prettier would do this anyway, but it’s separated out for a more
reviewable diff. Generated by ESLint.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
This gives them cache-compatible URLs, and also avoids some extra
copies of the sprite sheet images.
Comments on the Octopus emoji added by tabbott.
Signed-off-by: Anders Kaseorg <anders@zulipchat.com>