fix typo

Author: PI-Victor

README.md

@@ -1,6 +1,6 @@
 bootstrap running containers with systemd-nspawn with the help of Docker.  
 
-First edit the `Dockerfile` to your liking - by default its only a bare docker
+First edit the `Dockerfile` to your liking - by default it's only a bare docker
  hub opensuse:leap image.
 
 `sudo make build` - This will build the `Dockerfile` creating a systemd-nspawn