Simplify README
Simplify README

Replace "All the splits" sections with and "Overview" one that
has a semantic structure.

Co-authored-by: David O <1b173a4c17e13d4e4f47c072799fa57a5ab7e2ba@gmail.com>

LouisCAD/Splitties,LouisCAD/Splitties,LouisCAD/Splitties