GET projects for the suggestions section

- [x] Added to README
- [x] Saved in Postman

This request will return five projects of the contractor's category.

These projects will also not have any ContractorProjects - meaning they have not been shown in any other contractor's swipe screens.

Example Request:
```
GET https://fixup-backend.herokuapp.com/api/v1/projects?contractor_id=1&limit=5
```

Example Response:
```
Status: 200 OK
[
{
"id": 11,
"title": "Broken Pipe",
"description": "A pipe in my bathroom is leaky",
"category": "plumbing",
"user_before_picture": "brokenpipe.png",
"user_after_picture": null
},
{
"id": 12,
"title": "Broken Pipe",
"description": "A pipe in my bathroom is leaky",
"category": "plumbing",
"user_before_picture": "brokenpipe.png",
"user_after_picture": null
}, { ... }, { ... }, { ... }
]
```

Need a query for a group of five projects with that contractor's category
The project should be contractor_choice=0

Start with the README and saved Postman request, then locate the handler for GET /api/v1/projects. Verify the query for contractor_id and limit=5, and confirm that the response contains five projects matching the contractor's category with contractor_choice=0 and no prior ContractorProjects.

Written by the indexing model from the issue text.