Add keyboard.repeat-rate and keyboard.repeat-delay

Add option to let the users configure the keyboard repeat delay and
rate. Also change the default values to mimic the Xorg, which is
also the values used by default by the majority of the compositors.

Fixes: #7

resources/default-config.kdl

@@ -3,6 +3,14 @@
 
 input {
     keyboard {
+        // Control the repeat rate of the keyboard.
+
+        // Repeat delay in milliseconds.
+        repeat-delay 660
+
+        // Repeat rate in characters per second.
+        repeat-rate 25
+
         xkb {
             // You can set rules, model, layout, variant and options.
             // For more information, see xkeyboard-config(7).