Timeformat: Apply to new communities post header

[marcustyphoon]

Description

Applies timeformat to the timestamps in the new unique post header used in tumblr communities (communitiesRedpopPostChrome).

Not sure if this will break anything else, like mutual checker yes it does.

Is this actually... desirable? I mean, I assume so, though the aesthetics aren't great.

Testing steps

• Confirm that Timeformat works on community posts with the new header (feature flag enabled).

[marcustyphoon]

Ah, this might become more relevant than I realized.

[AprilSylph]

This is introducing some unnecessary height to the post header as-is... gonna see if I can fix it.

[AprilSylph]

Flex items being their own display type is so weird, always throws me off.

I'm gonna merge this now, but just to let you know, I am aware of this fuckass behaviour and will fix it with a Tumblr-side change in the coming week:

(The separator needs to stop being on the .timestamp::before and instead be its own element inside the .info so that it disappears when .info is collapsed to a width of zero, but that also means it will stay at the end of the line when we allow wrapping via the CSS I just committed here.)