tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "npm i",
      "type": "shell",
      "command": "cd webui && npm i"
    },
    {
      "label": "Parcel",
      "type": "npm",
      "script": "start",
      "dependsOn": "npm i",
      "isBackground": true,
      "problemMatcher": {
        "background": {
          "activeOnStart": true,
          "beginsPattern": "parcel serve",
          "endsPattern": "Built in"
        },
        "pattern": {
          "regexp": ".*"
        }
      },
      "path": "webui"
    },
    {
      "label": "Build Webui",
      "type": "npm",
      "script": "build",
      "path": "webui",
      "group": "build",
      "problemMatcher": [],
      "dependsOn": "npm i"
    },
    {
      "label": "Terminate Parcel",
      "command": "echo ${input:terminate}",
      "type": "shell",
      "problemMatcher": []
    }
  ],
  "inputs": [
    {
      "id": "terminate",
      "type": "command",
      "command": "workbench.action.tasks.terminate",
      "args": "Parcel"
    }
  ]
}