Use Option for time, and set DPMS on start

cosmic-idle-config/src/lib.rs

@@ -4,13 +4,13 @@ use serde::{Deserialize, Serialize};
 #[derive(Debug, Deserialize, Serialize, Clone, CosmicConfigEntry)]
 pub struct CosmicIdleConfig {
     /// Screen off idle time, in ms
-    pub screen_off_time: u32,
+    pub screen_off_time: Option<u32>,
 }
 
 impl Default for CosmicIdleConfig {
     fn default() -> Self {
         Self {
-            screen_off_time: 10 * 60 * 1000,
+            screen_off_time: Some(10 * 60 * 1000),
         }
     }
 }