load script after initial registry burst

This makes the logic of installing idle handlers and layout handlers a bit
cleaner and allows us to send wayland request from the script in the future.

README.md

@@ -1,8 +1,10 @@
 # riverguile
 
-Layout generator for the [river](https://github.com/riverwm/river) Wayland
-server which uses [Guile Scheme](https://www.gnu.org/software/guile/) for
-layouts. Its layout namespace is `riverguile`.
+Scripting layer for the [river](https://github.com/riverwm/river) Wayland
+server using [Guile Scheme](https://www.gnu.org/software/guile/).
+
+Send commands to river and install handlers for various events, inclusing
+layout events.
 
 Uppon launch, riverguile tries to load a scheme script and checks the following
 paths for it in the given order:
@@ -17,9 +19,15 @@ is available, which can be used to install handlers to certain events.
 Check the man page for more information.
 
 Here is an example `layout.scm` file replicating rivertiles behavior of having
-a main window and a stack of windows aside:
+a main window and a stack of windows aside while also automatically locking
+the screen after five minutes of inactivity.
 
 ```scheme
+(install-handler 'idle:300 (lambda (event)
+                             (cond ((eq? event 'idle) (system "swaylock &")
+                                                      (system "backlight.sh set-to 40"))
+                                   ((eq? event 'resume) (system "backlight.sh set-to 100")))))
+
 (define split 0.55)
 
 (define (layout:rows n x y w h)