Update project p5.js to 0.3.15

libgrabber updated project p5.js to 0.3.15.

@lmccart

### Metadata information

```json
{
  "metadata": {
    "packageManager": "github",
    "name": "p5.js",
    "repo": "lmccart/p5.js",
    "files": {
      "basePath": "lib/",
      "include": ["p5.min.js", "./addons/**/*"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/p5.js",
    "localVersions": ["0.3.0", "0.3.2", "0.3.3", "0.3.4", "0.3.5", "0.3.6", "0.3.7", "0.3.8", "0.3.9", "0.3.11", "0.3.12", "0.3.13", "0.3.14"],
    "remoteVersions": ["0.2.22", "0.2.23", "0.3.0", "0.3.2", "0.3.3", "0.3.4", "0.3.5", "0.3.6", "0.3.7", "0.3.8", "0.3.9", "0.3.11", "0.3.12", "0.3.13", "0.3.14", "0.3.15"],
    "branchVersions": []
  },
  "version": "0.3.15",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/p5.js/0.3.15",
  "branch": "p5.js/0.3.15"
}
```