Fix #534 respond support in view_submission listeners (it works only when response_url_enabled is true)

[seratch]

Summary

This pull request resolves #534 by adding respond support in app.view listeners.

see also:

• Fix #260 Enable to use respond utility in app.view listeners (only when response_urls exists) bolt-python#288
• Add support for response_urls in modals java-slack-sdk#405

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 #889 (4754b2a) into main (22f938e) will increase coverage by 0.08%.
The diff coverage is 100.00%.

❗ Current head 4754b2a differs from pull request most recent head 88c9109. Consider uploading reports for the commit 88c9109 to get more accurate results

@@            Coverage Diff             @@
##             main     #889      +/-   ##
==========================================
+ Coverage   66.11%   66.19%   +0.08%     
==========================================
  Files          13       13              
  Lines        1201     1204       +3     
  Branches      354      355       +1     
==========================================
+ Hits          794      797       +3     
  Misses        338      338              
  Partials       69       69              

Impacted Files	Coverage Δ
src/App.ts	82.91% <100.00%> (+0.14%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 22f938e...88c9109. Read the comment docs.

[mwbrooks]

Just for my own knowledge, are we only handling the first response_urls[0] because that keeps the functionality consistent with other areas of Bolt-JS that only handle the first response url?

[seratch]

@mwbrooks Good point. As of today, the response_urls can have only one element and we don't have any plans to have more elements in the short term. That's the reason why we can safely pick up the first element here, and thus far we can provide respond utility, which is consistent with other areas.

If the array start having multiple options in the future, we still can provide respond with the first element. When a developer would like to use a non-primary element, the right way to do so is to select the one from the array and then use axios directly with the URL. We may want to provide an easy-to-use utility for it.