Added testing for presence of a CITATION.cff

[jspaaks]

Description

In this branch we're working on adding a filter that uses the GitHub API to check that a file named "CITATION.cff" is present in the root of the repo.

Related issues:

• 2

• 3

Instructions to review the pull request

• Make a GitHub Access token here https://github.com/settings/tokens
• cp secrets.txt.example secrets.txt
• Update the value of GITHUB_TOKEN in secrets.txt
• install Node >= 14

• cd $(mktemp -d --tmpdir cffbot-XXXXXX)
  git clone https://github.com/cffbots/filtering .
  git checkout <this-branch>
  source secrets.txt
  node query.mjs

[jspaaks]

Thanks for the review!