Update project picturefill to 2.2.0-beta

libgrabber updated project picturefill to 2.2.0-beta.

@scottjehl

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "picturefill",
    "repo": "scottjehl/picturefill",
    "files": {
      "basePath": "dist/",
      "include": ["**/*"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/picturefill",
    "localVersions": ["1.2.1", "2.0.0", "2.1.0"],
    "remoteVersions": ["v1.0.0", "v1.1.0", "v1.2.0", "1.2.1", "2.0.0-alpha", "2.0.0-beta", "2.0.0", "2.1.0-beta", "2.1.0-beta2", "2.1.0", "2.2.0-beta"],
    "branchVersions": []
  },
  "version": "2.2.0-beta",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/picturefill/2.2.0-beta",
  "branch": "picturefill/2.2.0-beta"
}
```