Update readmes with the info of the old repos

[MauroToscano]

Update readmes with the info of the old repos

• Created a Readme, based in the old ones, for Cairo prover and Stark Prover.
• Updated main readme with a link to the documentation and added there references there.
• Added a Makefile to the cairo prover so the CLI can be run as it was run before
• Added missing make clean to main Makefile
• Add link to the provers in the main README so they are easier to access

[codecov-commenter]

Codecov Report

Merging #561 (3719e50) into main (912c7a6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #561   +/-   ##
=======================================
  Coverage   95.50%   95.50%           
=======================================
  Files         112      112           
  Lines       18904    18904           
=======================================
  Hits        18054    18054           
  Misses        850      850           

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