loadConfig searching should stop once projectRoot is reached

[mischnic]

🐛 bug report

Config searching should stop once projectRoot is reached.

🤔 Expected Behavior

Configs outside the project should not be read.

😯 Current Behavior

They are applied.

💻 Code Sample

.
├── .terserrc
└── project
    ├── dist
    │   ├── index.js
    │   └── index.js.map
    ├── index.js
    ├── package.json
    └── yarn.lock

{
  "compress": false,
  "mangle": false
}