Allow uploading individual files in the Web UI upload form

[rien]

We currently only accept ZIP-archives containing all the files.

Accepting multiple files or even selecting directories would not be difficult and would streamline the submission process in some cases.

[jorg-vr]

Would this mean that it becomes possible to add or replace files after report creation?

Maybe not relevant for this issue. But when discussing button placement for detecting plagiarism, Kristof mentioned that he would prefer to have no button at all, with everything happening in the background.
Seeing this issue made me think about live updates of the plagiarism detection every time a student submits... But I don't know enough about how dolos works to know if this is realistic

[rien]

Unfortunately not, the issue of updating a plagiarism report is a long term goal of Dolos and currently not immediately feasible. I've created an issue to track this: #1536.

However, it is completely feasible to run Dolos after the deadline of a series has passed.