install ubuntu 20.04 focal fossa

roles/netbootxyz/defaults/main.yml

@@ -497,6 +497,8 @@ releases:
     mirror: http://archive.ubuntu.com
     name: Ubuntu
     versions:
+    - code_name: focal
+      name: 20.04 LTS Focal Fossa
     - code_name: eoan
       name: 19.10 Eoan Ermine
     - code_name: bionic