Update project gridster.js to v0.5.6

libgrabber updated project gridster.js to v0.5.6.

@ducksboard

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "gridster.js",
    "repo": "ducksboard/gridster.js",
    "files": {
      "basePath": "dist/",
      "include": ["**/*"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/gridster.js",
    "localVersions": ["0.5.0", "0.5.2", "0.5.3", "0.5.4", "0.5.5"],
    "remoteVersions": ["v0.1.0", "v0.2.0", "v0.2.1", "v0.3.0", "v0.4.0", "v0.4.1", "v0.4.2", "v0.4.3", "v0.4.4", "v0.5.0", "v0.5.1", "v0.5.2", "v0.5.3", "v0.5.4", "v0.5.5", "v0.5.6"],
    "branchVersions": []
  },
  "version": "v0.5.6",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/gridster.js/0.5.6",
  "branch": "gridster.js/v0.5.6"
}
```