UBUNTU: [Packaging] update Ubuntu.md

BugLink: https://bugs.launchpad.net/bugs/1786013
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

Author: ksacilotto

Ubuntu.md

@@ -0,0 +1,8 @@
+Name:    linux
+Version: 5.4.0
+Series:  20.04 (focal)
+Description:
+    This is the source code for the Ubuntu linux kernel for the 20.04 series. This
+    source tree is used to produce the flavours: generic, generic-lpae, lowlatency.
+    This kernel is configured to support the widest range of desktop, laptop and
+    server configurations.