Add missing fields to PR stream

Nobody has claimed this yet.

Currently the PR stream is missing a bunch of key fields
```
additions
deletions
review_comments (int)
changed_files (int)
..etc
```
The current api route we use https://docs.github.com/en/rest/reference/pulls#list-pull-requests isn't sufficient to get all these missing fields. We would need to use the singular pr route https://docs.github.com/en/rest/reference/pulls#get-a-pull-request to fetch everything. This may be difficult since this would greatly increase the amount of requests made to the API. We could maybe cut this down by making a custom query with absolutely everything with #48.

Start by tracing the PR stream implementation and compare the fields available from the list pull requests route with the singular get-a-pull-request route in the linked GitHub API documentation. Review issue #48 for the possible custom query, then define a way to expose additions, deletions, review_comments, changed_files, and other required fields without an unacceptable increase in API requests.

Written by the indexing model from the issue text.