Add release notes of v1.8.1

[RainbowMango]

What type of PR is this?

/kind documentation

What this PR does / why we need it:

This PR adds release notes for the coming v1.8.1 releases.
See the full change log from here.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (df708ad) 51.79% compared to head (ee11792) 51.78%.

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Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.8    #4429      +/-   ##
===============================================
- Coverage        51.79%   51.78%   -0.01%     
===============================================
  Files              243      243              
  Lines            24110    24110              
===============================================
- Hits             12487    12485       -2     
- Misses           10942    10944       +2     
  Partials           681      681              

Flag	Coverage Δ
unittests	51.78% <ø> (-0.01%)	⬇️

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