Fix handlings of labelIDs

• #22
  • Needs to follow https://github.com/octokit/graphql.js/#variables changes in case if labelIds are multiple.

Run as JavaScript action instead of Docker container action

Refs:

• #21
  • https://help.github.com/en/actions/automating-your-workflow-with-github-actions/about-actions#types-of-actions
  • https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-a-javascript-action
  • https://github.com/actions/typescript-action#publish-to-a-distribution-branch

Adapt GitHub Actions v2

• #9
  • Use the official toolkit
    • Remove JasonEtco/actions-toolkit
  • Make this action work