Deploy the App to Heroku with one click

[bemau]

Summary

• Minor change allows users to deploy the app to Heroku with one click with the deploy template.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

Merging #1384 (ab3c428) into main (7db76e5) will not change coverage.
The diff coverage is n/a.

❗ Current head ab3c428 differs from pull request most recent head 70b406c. Consider uploading reports for the commit 70b406c to get more accurate results

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  Coverage   72.69%   72.69%           
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  Files          17       17           
  Lines        1465     1465           
  Branches      437      437           
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  Hits         1065     1065           
  Misses        310      310           
  Partials       90       90           

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[seratch]

Hi @MaurizioBella, thanks for submitting this PR! Utilizing heroku-buildpack-monorepo for deploying the sub directory template is so cool.

Ideally, we would like to avoid having app.json in this repository but it seems that having the file in the root directory is a requirement of "Deploy to Heroku" button.

The basic requirements for creating a button are that your app has a valid app.json file in its root directory, and that the app source code is hosted in a GitHub repository.
https://devcenter.heroku.com/articles/heroku-button#requirements

@stevengill @filmaj @misscoded @mwbrooks @srajiang
I myself am fine to merge this PR but I would like to know other maintainers' thoughts before merging it. For context, @srajiang suggested @MaurizioBella to send a pull request to this repo: slackapi/bolt-js-getting-started-app#11 (comment)

[srajiang]

Thanks for this @MaurizioBella!

[mwbrooks]

This is really nice @MaurizioBella, thanks for the pull request!

@seratch I agree, it would be nice to not have app.json in the repo's root directory but appears to be a requirement for Heroku.

[seratch]

Thanks for you all's reviews. I think that it's fine to merge this PR now. @MaurizioBella Thanks a lot for your contribution!

[seratch]

Before merging this, I'm waiting for the CI builds complete

[bemau]

Thanks for you all's reviews. I think that it's fine to merge this PR now. @MaurizioBella Thanks a lot for your contribution!
Absolutely, happy to contribute, and thanks, @srajiang, for pointing me to this repo. Great team-work!

[orozcoadrian]

Might be helpful to mention this new "one-click deployment to heroku" here: https://slack.dev/bolt-js/deployments/heroku
Let me know if you'd like me to open a PR.