Create PUT route for path '/api/description'

[CjJordan]

Create a PUT route the accesses the req.body and updates the userDesc in the db where the id matches.

This issue is complete when:

• [ ] A PUT route exists for path '/api/description'
• [ ] the route recieves the req.body
• [ ] the db is updated appropriately
• [ ] the new entry is returned to the front-end