[FEATURE] Download button on thumbnails shown on a user's media tab

[jaeo-k]

Is your feature request related to a problem? Please describe.
When I'm trying to download media from a certain user, it's kind of hard to see their original works from their POSTS tab since it includes retweets. So I move to the MEDIA tab, but to click every thumbnail before downloading is also a chore.

Describe the solution you'd like
To add a download button appearing at the thumbnails present in the MEDIA tab. Also to add a marker to indicate that this certain media has already been downloaded.

Describe alternatives you've considered
The alternative is to click every thumbnail, download it, and return to the MEDIA tab.

Additional context
Please check the screenshot attached, it's a script for Pixiv which I use to download arts without having to open the post.

[EltonChou]

Related to #126

Would be implemented in next major version.
Two bottom corners were occupied by time and multi-medias icon.
So we can only choose top corners to place the button.