TypeError: window.URL.createObjectURL is not a function

Hello!

I was hoping to use this in lieu of the Google Maps input. The studio is building fine and looks good but as soon as I run `sanity graphql deploy` I get this strange error:

```
TypeError: window.URL.createObjectURL is not a function
at define (~/coding/mindmapbc/sanity-studio/node_modules/mapbox-gl/dist/mapbox-gl.js:106:41)
at ~/coding/mindmapbc/sanity-studio/node_modules/mapbox-gl/dist/mapbox-gl.js:116:1
at ~/coding/mindmapbc/sanity-studio/node_modules/mapbox-gl/dist/mapbox-gl.js:84:81
at Object. (~/coding/mindmapbc/sanity-studio/node_modules/mapbox-gl/dist/mapbox-gl.js:87:2)
```

Which based on the googling that I have done seems to be something to do with mapbox and testing? See this issue:

https://github.com/mapbox/mapbox-gl-js/issues/3436

Here is my are my dependencies in case it helps:
```
"dependencies": {
"@sanity/base": "^2.0.7",
"@sanity/code-input": "^2.0.5",
"@sanity/color-input": "^2.0.5",
"@sanity/components": "^2.0.7",
"@sanity/core": "^2.0.5",
"@sanity/dashboard": "^2.0.5",
"@sanity/default-layout": "^2.0.7",
"@sanity/default-login": "^2.0.5",
"@sanity/desk-tool": "^2.0.8",
"prop-types": "^15.6",
"react": "^16.2",
"react-dom": "^16.2",
"react-icons": "^3.11.0",
"sanity-plugin-dashboard-widget-document-list": "^0.0.11",
"sanity-plugin-mapbox-input": "^0.0.3",
"sanity-plugin-media": "^0.4.0"
},
"devDependencies": {}
}
```

And sanity.json stuff

```
"plugins": [
"@sanity/dashboard",
"@sanity/base",
"@sanity/components",
"@sanity/default-layout",
"@sanity/default-login",
"@sanity/desk-tool",
"@sanity/color-input",
"@sanity/code-input",
"dashboard-widget-document-list",
"dashboard-widget-structure-menu",
"media",
"mapbox-input"
],
"parts": [
{
"name": "part:@sanity/base/schema",
"path": "./schemas/schema.js"
},
{
"name": "part:@sanity/desk-tool/structure",
"path": "./structure/deskStructure.js"
},
{
"implements": "part:@sanity/dashboard/config",
"path": "./dashboard/dashboardConfig.js"
}
]
```