Set current version to 5.x in README and highlight changes

[timtebeek]

As requested.

[timtebeek]

@TimvdLippe feel free to edit or make suggestions on this pull request.

[TimvdLippe]

Thanks!

[codecov-commenter]

Codecov Report

Base: 84.76% // Head: 84.78% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (14783b5) compared to base (adf528d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2867      +/-   ##
============================================
+ Coverage     84.76%   84.78%   +0.02%     
- Complexity     2867     2868       +1     
============================================
  Files           327      327              
  Lines          8780     8780              
  Branches       1068     1068              
============================================
+ Hits           7442     7444       +2     
+ Misses         1064     1063       -1     
+ Partials        274      273       -1     

Impacted Files	Coverage Δ
src/main/java/org/mockito/Mockito.java	96.42% <ø> (ø)
...creation/bytebuddy/SubclassByteBuddyMockMaker.java	50.00% <0.00%> (+2.70%)	⬆️

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