Added Link to make readthedocs Documentation Webpage easier to find by putting it into the main README file
Added Link to make readthedocs Documentation Webpage easier to find by putting it into the main README file

Signed-off-by: Davide <f7b32570f1f947129750c043f17cbe06afc492b0@stud.tu-darmstadt.de>

SymbiFlow/symbiflow-website,SymbiFlow/symbiflow-website,SymbiFlow/symbiflow-website