docs: redirect links to the current developer documentation pages

[zimeg]

Summary

This PR redirects links to the current developer documentation pages 📚 ✨

• The "api.slack.com" pages are replaced unless toward app settings
• The "tools.slack.dev" pages are changed to "docs.slack.dev/tools"
• Pages published to the docs site use relative links for fast navigation

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.86%. Comparing base (3493f18) to head (5cf21e5).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #532   +/-   ##
=======================================
  Coverage   99.86%   99.86%           
=======================================
  Files           7        7           
  Lines         722      722           
=======================================
  Hits          721      721           
  Misses          1        1           

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[zimeg]

@haleychaas Incredible thanks to better navigation around these pages! Let's merge this! 📠 ✨