config: implement shortcut latching

toml-spec/spec/spec.yaml

@@ -2131,3 +2131,24 @@ ComplexShortcut:
         The action to execute.
         
         Omitting this is the same as setting it to `"none"`.
+    latch:
+      ref: Action
+      required: false
+      description: |
+        An action to execute when the key is released.
+        
+        This registers an action to be executed when the key triggering the shortcut is
+        released. The active modifiers are ignored for this purpose.
+        
+        - Example:
+        
+          To mute audio while the key is pressed:
+        
+          ```toml
+          [complex-shortcuts.alt-x]
+          action = { type = "exec", exec = ["pactl", "set-sink-mute", "0", "1"] }
+          latch = { type = "exec", exec = ["pactl", "set-sink-mute", "0", "0"] }
+          ```
+        
+          Audio will be un-muted once `x` key is released, regardless of any other keys
+          that are pressed at the time.