add documentation for socket mode and developer mode

[TheManWhoStaresAtCode]

Summary

Provide some basic documentation of the developer mode - as far as I understand it from the provided information in #714 and #742. Is related to #749.
As I mention the undocumented socket mode I documented this option as well.

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 #1218 (c945e7a) into main (4158bc5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1218   +/-   ##
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  Coverage   73.20%   73.20%           
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  Files          17       17           
  Lines        1437     1437           
  Branches      431      431           
=======================================
  Hits         1052     1052           
  Misses        300      300           
  Partials       85       85           

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[filmaj]

Hey, this is great, thank you for the pull request! I left a couple of minor grammar / phrasing tweaks.

This is great first step for #749, but I think this alone doesn't resolve that issue. I agree with @stevengill's opinion in #749 that we should also expand the guide / tutorial docs. I'll leave some ideas on that in #749 - if you'd like to take a stab at writing that as well, we would welcome any additional pull requests!

[filmaj]

Thanks for addressing the changes and the PR! Very much appreciated 🙏