Support upload by dragging files to exercise name

[yammesicka]

[ron-huberfeld]

@yammesicka can I handle this one?

[yammesicka]

Sure.

• [ ] Be sure to have some feedback ondragover - something like the border goes dotted instead of solid.
• [ ] The element should be updated on real time - no page refreshes.
• [ ] It should be able only on the main page (and disabled on the 'archive' page)

Also, we should think about how to indicate (on the UX perspective) the following scenarios:

• [ ] Success
• [ ] Upload in progress
• [ ] Failed to upload

[ron-huberfeld]

@yammesicka can you define the dropzone location? - is it a new button, the existing button or all the exercise area section?

[yammesicka]

The whole exercise area :)