Rolf Schäuble

Make it safe for klippy:ready handlers to execute UPDATE_DELAYED_GCODE

4

When another klippy:ready handler executes UPDATE_DELAYED_GCODE before DelayedGcode's ready handler runs, then `self.timer_handler` is None, causing the `update_timer` to fail.

Extend documentation of klippy:connect and klippy:read event handlers.

3

Describe more clearly what is and what isn't allowed in the klippy:connect and klippy:ready event handlers.