Trello integration action

Connects GitHub PRs and Trello cards:

• attaches PR link to a Trello card (works best with GitHub Power-up),
• moves Trello card when PR is opened or closed,
• adds an appropriate board label to a Trello card when branch name is categorised (e.g. feature/foo) and Trello card already doesn't have a label.

The action looks for Trello card URL within the Pull Request description and comments. If found, it will integrate the two worlds.

name: Trello integration
on:
    pull_request:
        types: [opened, edited, closed]
    issue_comment:
        types: [created, edited]
jobs:
    build:
        runs-on: ubuntu-latest
        steps:
            - uses: rematocorp/trello-integration-action@main
              with:
                  github-token: ${{ secrets.GITHUB_TOKEN }}
                  trello-api-key: ${{ secrets.TRELLO_API_KEY }} # https://trello.com/app-key
                  trello-auth-token: ${{ secrets.TRELLO_AUTH_TOKEN }} # https://trello.com/app-key then click generate a token
                  trello-list-id-pr-open: ${{ secrets.TRELLO_PR_OPEN_LIST_ID }} # Trello list ID for open pull request, visit a board then append .json to url to find id
                  trello-list-id-pr-closed: ${{ secrets.TRELLO_PR_CLOSED_LIST_ID }} # Trello list ID for closed pull request, visit a board then append .json to url to find id

Inspired by dalezak/github-commit-to-trello-card and delivered/attach-to-trello-card-action.