Add a basic README to mlag demo
Add a basic README to mlag demo

jordant/cumulus-vx-vagrant,gchami/cumulus-vx-vagrant,zioproto/cumulus-vx-vagrant,benthomasson/cumulus-vx-vagrant,mirzawaqasahmed/cumulus-vx-vagrant,jordant/cumulus-vx-vagrant,gchami/cumulus-vx-vagrant,benthomasson/cumulus-vx-vagrant,mirzawaqasahmed/cumulus-vx-vagrant,Mierdin/cumulus-vx-vagrant,mirzawaqasahmed/cumulus-vx-vagrant,jordant/cumulus-vx-vagrant,Mierdin/cumulus-vx-vagrant,gchami/cumulus-vx-vagrant,benthomasson/cumulus-vx-vagrant,zioproto/cumulus-vx-vagrant,Mierdin/cumulus-vx-vagrant,zioproto/cumulus-vx-vagrant