add debug configuration for firefox

.vscode/launch.json

@@ -29,11 +29,29 @@
         "request": "launch",
         "name": "Debug: Chrome",
         "sourceMaps": true,
-        "webRoot": "${workspaceFolder}/public",
         "sourceMapPathOverrides": {
           "webpack:///*": "${workspaceFolder}/*"
         },
+        "webRoot": "${workspaceFolder}/public",
         "url": "http://localhost:3000"
+      },
+      {
+        "type": "firefox",
+        "request": "launch",
+        "name": "Debug: Firefox",
+        "reAttach": true,
+        "url": "http://localhost:3000",
+        "webRoot": "${workspaceFolder}/public",
+        "pathMappings": [
+          {
+            "url": "webpack:///src",
+            "path": "${workspaceFolder}/src"
+          },
+          {
+            "url": "http://localhost:3000",
+            "path": "${workspaceFolder}/public"
+          }
+        ]
       }
     ]
 }