add vscode launch task

.vscode/launch.json

@@ -0,0 +1,20 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Debug Test",
+            "env": {
+                "ABLY_ENV": "sandbox",
+            },
+            "cwd": "${workspaceFolder}",
+            "runtimeExecutable": "node",
+            "runtimeArgs": ["--inspect-brk=9229", "node_modules/.bin/grunt", "test"],
+            "port": 9229
+        }
+    ]
+}