support PRs for public repos

[ryanatkn]

• change gro packages to call github API - https://docs.github.com/en/rest/pulls/pulls#list-pull-requests
• add auth token
• conditional requests and 304 handling - https://docs.github.com/en/rest/overview/resources-in-the-rest-api#conditional-requests
• automate auth token
• figure a way around the env init issue in CI
• load closed PRs and filter unfinished tasks