docs: redirect issue tracker template option links

[zimeg]

Changelog

N/A - Settings for this repository 🐙

Summary

This PR redirects issue tracker template option links to the format introduced in #488 📚

Preview

• https://github.com/slackapi/slack-cli/blob/3923e918cffe2e48571c35be862b9a301134fb0a/README.md#hammer_and_wrench-contributions

Testing

🔍 Confirm these links arrive to expected pages please!

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 71.29%. Comparing base (f99323b) to head (6467151).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #510      +/-   ##
==========================================
+ Coverage   71.25%   71.29%   +0.04%     
==========================================
  Files         222      222              
  Lines       18682    18682              
==========================================
+ Hits        13312    13320       +8     
+ Misses       4189     4185       -4     
+ Partials     1181     1177       -4     

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[mwbrooks]

Thanks @zimeg! Good catch on the URL.