docs: translate image reference in README.md
docs: translate image reference in README.md

Change the reference from github md format to sphinx rst
including the file in the docs tree.

roolebo/pyroute2,tomislacker/python-iproute2,drzaeus77/pyroute2,roolebo/pyroute2,drzaeus77/pyroute2,mtiny/pyroute2,mtiny/pyroute2,tomislacker/python-iproute2