Add note for cni versions compatibility

[bmangoen]

What type of PR is this?

• Enhancement / New Feature
• Bug Fix
• Refactor
• Optimization
• Test
• Documentation Update

What this PR does / why we need it:

Document IstioCNI and Istio versions compatibility

Which issue(s) this PR fixes:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.60%. Comparing base (05daafb) to head (58a2876).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #525      +/-   ##
==========================================
- Coverage   75.76%   75.60%   -0.17%     
==========================================
  Files          39       39              
  Lines        2476     2476              
==========================================
- Hits         1876     1872       -4     
- Misses        510      513       +3     
- Partials       90       91       +1     

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