Update docs using changes from napari/docs

[Czaki]

Description

In this PR, I backport changes from napari/docs repository made after the docs split.

References

Type of change

• Maintenance (changes required to run napari, tests, & CI smoothly)

How has this been tested?

• example: the test suite for my feature covers cases x, y, and z
• example: all tests pass with my change
• example: I check if my changes works with both PySide and PyQt backends
  as there are small differences between the two Qt bindings.

Final checklist:

• My PR is the minimum possible work for the desired functionality
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• If I included new strings, I have used trans. to make them localizable.
  For more information see our translations guide.

[codecov]

Codecov Report

Merging #5979 (f9fb312) into v0.4.18x (9d81fec) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           v0.4.18x    #5979      +/-   ##
============================================
- Coverage     88.65%   88.63%   -0.02%     
============================================
  Files           620      620              
  Lines         52516    52516              
============================================
- Hits          46559    46550       -9     
- Misses         5957     5966       +9     

see 4 files with indirect coverage changes