#3 Resolves "Implement offline task submission"

Closes #26 (closed)

Notes of change:

Added new marketplace/submission page to the frontend. Removed other/ page. Added API call at api/user/username/marketplace/submission which accepts PUT requests of an image file (list of acceptable files cause be found at the tops of utils and views) encoded as base64, the files extension, a description and slogan. Also added a loading icon that shows until the page passes loaded={true} props to the basepage.

Demonstration:

Screen_Recording_2021-11-23_at_03.38.14

Notes of implementation:

Have left areas that the description and slogans can be added to the models in as unable to implement currently. Additionally, the milestone completion isn't being handled, as it too is waiting on the models from csp4.

CSS could also do with being cleaned-up but I'm of the onion that that will be done once the proper database API is added as its not production-ready anyways. Also the wireframes haven't been finished as of yet so any CSS written rn is subject to change

Also, the tests do create and delete actual /media/ directories and files, so we have to make sure that users cannot choose the name foo or bar. I think this will deal with itself as you shouldn't really run tests in the production environment unless absolutely necessary, and users will all have @ symbols in their name due to how we are constructing the unique username/login keys.