cleanup/README: add help page (#129)

README.md

@@ -10,3 +10,28 @@
 
 > **NOTE**: ABRoot v2 is currently in development. The current
 > version is v1, which is available in the `v1` branch.
+
+## Help
+
+```md
+ABRoot provides full immutability and atomicity by performing transactions between 2 root partitions (A<->B)
+
+Usage:
+  abroot [command]
+
+Available Commands:
+  completion  Generate the autocompletion script for the specified shell
+  help        Help about any command
+  kargs       Manage kernel parameters
+  pkg         Manage packages
+  rollback    Return the system to a previous state
+  status      Display status
+  upgrade     Update the boot partition
+
+Flags:
+  -h, --help      help for abroot
+  -v, --verbose   Show more detailed output
+      --version   version for abroot
+
+Use "abroot [command] --help" for more information about a command.
+```