[tumblr] attempt to fetch high-quality inline images

[the-blank-x]

Fixes #1846, and fixes #1344

[Hrxn]

Isn't ../s2048x3072/.. the maximum anyway?
Or did they change their site again?

[the-blank-x]

What do you mean?

[mikf]

Isn't ../s2048x3072/.. the maximum anyway?

Tumblr supports images larger than that. Not entirely sure since when that was a thing again, but this issue from October 2020 talks about downloading a 2874x1761 version of an image, which exceeds 2048x3072.

This post contains a 6400x4000 monochrome PNG and gallery-dl can now actually download that, but only when it's a photo post.

This PR would make it possible to grab higher resolution inline images.

[mikf]

@the-blank-x would it be OK I personally change some of your code around? I would like to re-structure some of it and explaining this would take quite a bit longer than just doing it myself. (This is a general problem with most PRs, in my opinion, but oh well ...)

Also, are you still allowed to change this PR's title, after I as repo owner edited it?

[the-blank-x]

would it be OK I personally change some of your code around?

Sure

are you still allowed to change this PRs title, now that I as repo owner have edited it?

The button is there, but it doesn't work and it seems that the site is broken on my phone