Add deployment guide for Heroku

[zimeg]

Summary

The steps needed to deploy a next-generation Bolt app to Heroku are captured in this guide [HERMES-3369], as well as a few tips for ongoing app development. All suggestions, comments, missing points, or anything else is most welcomed!

A few notes

• This guide links out to other guides in the prerequisites section in the interest of brevity.
• Both the steps for Socket Mode apps and apps using the standard web connection are covered.
• A neat point (imo) about link trigger functionality in this deployed environment is noted.

Reviewers

To review the changes to the docs, check out the "Generating documentation" documentation then head to http://localhost:4000/bolt-js/future/deploy-your-app.

Requirements

• 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 #1617 (81afa8a) into main (3b5f084) will not change coverage.
The diff coverage is n/a.

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##             main    #1617   +/-   ##
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  Coverage   82.09%   82.09%           
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  Files          18       18           
  Lines        1502     1502           
  Branches      437      437           
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  Hits         1233     1233           
  Misses        172      172           
  Partials       97       97           

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[hello-ashleyintech]

Excellent work, I'm loving the voice and tone of the guide and how thorough it is! Left some feedback and questions, let me know if you'd like to sync up on any of them or feel free to drop me a message 😄 Also sorry for the stray comments! I kept accidentally submitting them instead of putting them all in the same review 🤦

[hello-ashleyintech]

Wonderful work and thank you for making those changes! 🙌 I dropped a few more suggestions, let me know your thoughts and if you have any questions!

[hello-ashleyintech]

Excellent work, this worked like a charm! ✨ I ran through this again and left some suggestions here and there. Feel free to reject or accept suggestions as you see fit, and definitely let me know if there are any questions! 😄

[hello-ashleyintech]

after reading through this again - what are your thoughts on updating this header title to make it more explicit that this is only a required step if your app isn't using socket mode? I'm not sure what that would look like, maybe something like "Settings for apps not using Socket Mode" but with a bit more indication about what's inside this section?

[hello-ashleyintech]

Looks great to me! 🙌 🚀