List user's open cpython PRs, add "get info from PR" button

[cmaloney]

At PyConUS in the sprints and hoping to make some workflow improvements based on new developers using blurb. Can split into multiple issues, but high level:

1. List the most recent open CPython PRs by the user (limited to a smallish number)
2. Add a "fetch" button so given the github PR number can get information on it (github issue, if there is an existing blurb). Limit the max "fetch file" size. (This same infra used for "click on PR -> get info)
3. Be able to update an existing blurb in the PR (simple edits without having to figure out git workflow)

Happy to split into multiple smaller issues/prs. If any of these are outside scope of the blurb-it app let me know

[Mariatta]

I think this is a great idea!

[Mariatta]

Yes splitting into different PRs sounds good as well. Please do prepare a PR (or multiples) to address this ticket. Thank you.

[cmaloney]

Currently working on / current draft UI (Button to "load" the current issue, dropdown for recent issues by the user)