Add bookmarklet support for Marvel comic covers

[HeeroWingZero]

While the on-topicness of official western comic covers is up to debate, there are guest variant covers by Japanese manga/anime artists hosted in good quality here (often not posted elsewhere).

Note that a comic listing can have multiple artists, the one labeled as "Penciler" seems to be who is considered the main artist on a listing (and listings can have multiple pencilers). Penciler credits will show up on an artist's creator page, while cover artist credits will not - as a result, the linked artist may not always be correct in the case of guest covers where a different artist did the cover page.

Example artist:
https://www.marvel.com/comics/creators/13682/peach_momoko

Example listing:
https://www.marvel.com/comics/issue/112999/ultimate_x-men_2024_3

Example sample:
https://cdn.marvel.com/u/prod/marvel/i/mg/9/40/65d73ad1ca961/portrait_uncanny.jpg

Example direct:
https://cdn.marvel.com/u/prod/marvel/i/mg/9/40/65d73ad1ca961/clean.jpg

Variant cover listings have slightly different URLs from primary covers.

Variant example:
https://www.marvel.com/comics/issue/102466/the_amazing_spider-man_2022_3_variant/variant

Variant sample:
https://cdn.marvel.com/u/prod/marvel/i/mg/6/d0/629e240f5be95/portrait_uncanny.jpg

Variant direct:
https://cdn.marvel.com/u/prod/marvel/i/mg/6/d0/629e240f5be95/clean.jpg

[HeeroWingZero]

Additional note - upon further inspection it turns out cover artist credits can be seen on an artist's creator page - there is a "Show Variants" option that is turned off by default. Could potentially be possible for a Variant listing to grab that credit as the artist to avoid incorrectly crediting the artist listed as Penciler instead of the guest cover artist.

Additionally there are also article pages on the site - these can contain comic covers (sometimes in higher res than the comic listing), concept art, and/or textless previews of interior art.

Example article:
https://www.marvel.com/articles/comics/ultraman-x-avengers-kyle-higgins-mat-groom-francesco-manna

Article sample:
https://cdn.marvel.com/content/1x/ultramxaven2024001_cov_0.jpg

Article direct (according to maxurl):
https://cdn.marvel.com/content/2x/ultramxaven2024001_cov_0.jpg

Here's another example of an article that includes a gallery with slides. Note that the images in the gallery each have their own captions but do not have separate URLs to link to them individually:
https://www.marvel.com/articles/comics/look-inside-avengers-tech-on-1-preview-pages