Cloud storage for documents

**Add files**
Add documents for workshop levels in addition to text

**Task List**

- [x] Setup cloud storage (hierarchy should mirror Firestore setup)
- [x] Add UI to save a file and remove a file that the user has added
- [ ] Add UI to display files that the user has uploaded for a workshop level
- [ ] User side display link to download file (or maybe an icon that represents file type for a clean look)
- [ ] Allow admin to set a name for the file they uploaded which can be displayed instead of a link

**Additional context**
Files can be anything --> powerpoints, pdfs, etc