adding drag in network map

frontend/assets/js/app.js

@@ -1166,6 +1166,14 @@ function getShapeResizeHandleAt(mx, my) {
 }
 
 function onMouseDown(e) {
+    if (e.button === 2) {
+        isPanning = true;
+        panStartX = e.clientX;
+        panStartY = e.clientY;
+        canvas.style.cursor = 'grabbing';
+        return;
+    }
+    if (e.button !== 0) return;
     const rect = canvas.getBoundingClientRect();
     const mx = e.clientX - rect.left - panX;
     const my = e.clientY - rect.top - panY;