Fix links in documentation, add CI test

[breqdev]

• Fix links in the documentation that were broken in Refactor Cpu and System traits #40
• Make sure we fail CI when invalid links in documentation exist

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (607b17f) 27.31% compared to head (8730f80) 27.31%.

Files	Patch %	Lines
src/lib.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #41   +/-   ##
=======================================
  Coverage   27.31%   27.31%           
=======================================
  Files          44       44           
  Lines        9055     9055           
=======================================
  Hits         2473     2473           
  Misses       6582     6582           

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[ava-silver]