Update Zigbee specifications and links in README

[Hedda]

Proposed change

Update Zigbee specifications and links in README.

Additional information

Device diagnostics

Checklist

• The changes are tested and work correctly
• pre-commit checks pass / the code has been formatted using Black
• Tests have been added to verify that the new code works
• Device diagnostics data has been attached

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.60%. Comparing base (b139f81) to head (3a62152).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev    #5256   +/-   ##
=======================================
  Coverage   92.60%   92.60%           
=======================================
  Files         424      424           
  Lines       14667    14667           
=======================================
  Hits        13582    13582           
  Misses       1085     1085           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.