feature: ECTS generation

- add update method to increase ECTS balance over time when player is at desk

src/ects.py

@@ -10,3 +10,13 @@ class ECTS:
         self.ects_per_second = START_ECTS_VALUE
         # timer when last ECTS was given to player
         self.last_update_time = pygame.time.get_ticks()
+
+    # check if ECTS should be added
+    def update(self, is_at_desk):
+        current_time = pygame.time.get_ticks()
+
+        # if player is at desk and interval passed
+        if is_at_desk and ((current_time - self.last_update_time) >= ECTS_UPDATE_INTERVAL):
+            self.ects_balance += self.ects_per_second
+            # reset timer
+            self.last_update_time = current_time