fixes panorama on tagged pages and liked feed

[theIncandescentAnteater]

Description

i believe this fixes #1785. as far as i can see, the extension already works on the community feeds.

the classes on the tagged page differ from the dash, but the liked page doesn't have a main element at all

Before	After

Testing steps

1. Load the modified addon
2. Go to a tagged page
3. See the wide post width
4. Go to a the likes feed
5. See the wide post width

[marcustyphoon]

For clarity, the communities bullet point in the linked issue points specifically to https://www.tumblr.com/communities, the single "community posts" feed that contains posts from all of your communities, and individual community posts viewed alone! Panorama does indeed already work in individual community feeds.

[marcustyphoon]

Setting a maximum post width (maxPostWidthVar) is working here on tagged pages, but not on the liked page!

[theIncandescentAnteater]

thanks! i wasn't in any communities so i didn't even realize that was it's own feed

the max post width on the communities page is a little weird, but i couldn't figure out a better way. there very well may be one though.

this is what it looks like with a max width less than the full width (the grid column is still max width, so the sidebars are still pushed all the way out).

panorama on communities feed (without restrictive max post width)

[marcustyphoon]

Hm, yeah, I bet there's a way to adjust the size natively. Tumblr's grid-template-columns value is 556px minmax(280px,360px) before we override it; surely we can make our override the same thing but with maxPostWidthVar inserted?

[theIncandescentAnteater]

overriding with maxPostWidthVar meant that posts were becoming wider than the screen. i'm sure there's a neat way to do it with a grid, but i just ended up adjusting it to mimic the flex layout of the other feeds.

[marcustyphoon]

Hm, would something like grid-template-columns: minmax(556px, var(${maxPostWidthVar})) minmax(280px,360px); work?