chore: Add .github/CODEOWNERS file

[mwbrooks]

Summary

This pull request adds a .github/CODEOWNERS file to adhere to the Salesforce Open Source project requirements. I've also added the JavaScript team and Education team as code owners to match https://github.com/slackapi/slack-cli.

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.

[mwbrooks]

Thanks for the review @misscoded 🙇🏻

Looks like all of our GitHub Checks are failing. The failures aren't related to this PR, but look like something TypeScript related 🤔

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.44%. Comparing base (eaf113a) to head (5c31d01).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2718   +/-   ##
=======================================
  Coverage   93.44%   93.44%           
=======================================
  Files          37       37           
  Lines        7674     7674           
  Branches      669      669           
=======================================
  Hits         7171     7171           
  Misses        498      498           
  Partials        5        5           

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[mwbrooks]

@misscoded Thanks for helping to resolve these failures! 🙌🏻 🙇🏻