Update readme

README.md

@@ -2,4 +2,21 @@
 A [maubot](https://github.com/maubot/maubot) that sends clickable markdown formatted links when it sees RT ticket numbers in a given format.
 
 ## Usage
-`rt123456` - Responds with `[123456](https://rt.phys.ethz.ch/rt/Ticket/Display.html?id=123456)`
+- `rt123456` - Responds with `[123456](https://rt.phys.ethz.ch/rt/Ticket/Display.html?id=123456)`
+- `!rt` - Show the help
+
+```
+Usage: !rt <subcommand> [...]
+
+    properties <ticket number> - Show all ticket properties.
+    resolve <ticket number> - Mark the ticket as resolved.
+    open <ticket number> - Mark the ticket as open.
+    stall <ticket number> - Mark the ticket as stalled.
+    delete <ticket number> - Mark the ticket as deleted.
+    autoresolve - Enable automatic ticket resolve mode.
+    comment <ticket number> <comment text> - Add a comment.
+    history <ticket number> - Get a list of all history items for a given ticket.
+    entry <ticket number> <history entry number> - Gets the history information for a single history entry.
+    last <ticket number> - Gets the history information for the last history entry.
+    show <ticket number> - Show all information about the ticket.
+```