Update getting started guide, migrate create new app guide, and rearrange nav (next gen)

[hello-ashleyintech]

Summary

The goal of this PR is to achieve the following docs updates:

• The getting started guide should focus on the starter template (hello world example) and get you to slack create, slack run, and slack trigger create, and then have folks to run the function
• Move the Create New App (Request Time Off app) into a tutorial on the Bolt JS site and move to bottom of nav (also added a redirect when updating the path)
• Move the migration guide to the bottom of the section

In a following PR, I will focus on standardizing examples across functions, triggers, and workflows pages to focus on the Hello World example so it is more coherent. That PR may also contain a separate page on interactivity.

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 #1603 (e99c83a) into main (4ec194b) will not change coverage.
The diff coverage is n/a.

❗ Current head e99c83a differs from pull request most recent head 2237fdf. Consider uploading reports for the commit 2237fdf to get more accurate results

@@           Coverage Diff           @@
##             main    #1603   +/-   ##
=======================================
  Coverage   82.01%   82.01%           
=======================================
  Files          18       18           
  Lines        1496     1496           
  Branches      436      436           
=======================================
  Hits         1227     1227           
  Misses        172      172           
  Partials       97       97           

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[srajiang]

@ashleymcm @stevengill - These refinements look good to me! Thoughts on relocating the entire section to above Basic concepts in a future PR so that it's a bit more "above the fold"?

[hello-ashleyintech]

I like the idea to make it higher visibility! 👍 One thought is, would it be confusing to put it as the first heading under "Getting Started" and "Reference" since the Getting Started guide still covers the non next-gen concepts and it's listed at the top? @srajiang @stevengill

[hello-ashleyintech]

Merging this in! In a following PR, I will focus on standardizing examples across functions, triggers, and workflows pages to focus on the Hello World example so it is more coherent. That PR may also contain a separate page on interactivity. We may also add in the update mentioned above with rearranging the nav depending on the decision made there! ✅

[stevengill]

Love it! Big improvements

[stevengill]

So it gets auto saved in the workflows directory in the bookmarks bar now. We should update this message to reflect that

[hello-ashleyintech]

Will do! I started the branch for additional updates, so added that in there!

[stevengill]

Personally, i'd keep this getting started guide where it is for now. We can discuss moving it more top level closer to GA