Update 'README.md'

README.md

@@ -1,7 +1,11 @@
 cgminer-gekko OpenWRT builder (work in progress)
-install ubuntu 16.04
+
+For mr3020 , wr703n , rpi , rpi2 => install ubuntu 16.04
+For mr3040 , wr802n , rpi3 => install ubuntu 20.04
+
 
 open terminal
+
 sudo apt-get update
 sudo apt-get install git -y
 sudo ./prereq.sh