docs: update changelog for 5.12.0

[MuyangAmigo]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.04%. Comparing base (1b199d8) to head (654c75e).
Report is 4 commits behind head on release/5.12.

Additional details and impacted files

@@              Coverage Diff               @@
##           release/5.12   #12901    +/-   ##
==============================================
  Coverage         90.04%   90.04%            
==============================================
  Files               577      577            
  Lines             34198    34198            
  Branches           6685     6823   +138     
==============================================
  Hits              30794    30794            
  Misses             1501     1501            
  Partials           1903     1903            

[sffamily]

looks good, so the content is largely the same as the pre-release and blog.