Added HotkeyDetector interface

src/model/HotkeyDetector.java

+package model;
+
+public interface HotkeyDetector {
+    /**
+     * Detects if a hotkey with the given id was pressed.
+     * @param id The id of the hotkey which is checked.
+     * @return If the hotkey was pressed.
+     */
+    boolean wasPressed(int id);
+}