[FEAT]: Support overriding github api url in create-github-app-token github action

[Harsh Trivedi]

Describe the need

Reference from discussion
I was creating an access token for a github app installed in a different organization and repository. I learned about https://github.com/actions/create-github-app-token#create-a-token-for-all-repositories-in-another-owners-installation.

Similar to the baseUrl option in Octokit constructor, it would be great if we could specify the github API url as an input to this action

      - uses: actions/create-github-app-token@v1
        id: get-access-token
        with:
          app-id: APP_ID
          private-key: PRIVATE_KEY
          base-url: https://slack-github.com/api/

I tried creating an access token for my github app installed in a different organization by specifying the owner and repository using the following:

      - uses: actions/create-github-app-token@v1
        id: get-access-token
        with:
          app-id: APP_ID
          private-key: PRIVATE_KEY
          owner: "owner"
          repositories: |
            owner/repo_name

However, the default github API hostname/url is set to api.github.com and we cannot change it to a custom hosted github installation.

Code of Conduct

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[github-actions]

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[Gregor Martynus]

closing in favor of actions/create-github-app-token#77. The issue is not related to octokit, let's discuss over at the repository of the GitHub Action itself