Add pointer lock key combo

Fixes #737

app/streaming/input/keyboard.cpp

@@ -126,6 +126,13 @@ void SdlInputHandler::performSpecialKeyCombo(KeyCombo combo)
         break;
     }
 
+    case KeyComboTogglePointerRegionLock:
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "Detected pointer region lock toggle combo");
+        m_PointerRegionLockActive = !m_PointerRegionLockActive;
+        updatePointerRegionLock();
+        break;
+
     default:
         Q_UNREACHABLE();
     }