Adds the possibility to include metadata when loading the client

[gabrielmagno]

When loading the renderer client, it would be great to have the option to include a metadata to send to the AVTransport. The metadata could include several information, like title, cover image, description, and even subtitle.

I simply included a new option value called "metadata", that could be passed in the options object when calling the load function.

[gabrielmagno]

Thank you for accepting my merge! Following on this, could the version be bumped to 0.0.3?

[thibauts]

And done

[gabrielmagno]

Awesome!