[FEATURE] Add data property to Event

[juanmiguelbesada]

Hi all!

I'm working with this library for a while (It works like a charm BTW), and I really missing what I think is a good new feature.

The default Event model, does not have the possibility to hold a "data" (Where data is whatever you need, it could be an object, an array or a primitive), and you always have to extend default Entity to include your custom data.

While i think this is good for advanced use cases, i think for simple use cases, having a "bag" where store whatever you need (a title, a status, or even an array with more complex data) without having to extend the default model would be perfect.

I don't know what you think, if you agree I can work on a pull request.

Thanks you for your work

[peter279k]

Hi, thank you for your reply.

If possible, you can just submit the PR and wait for @yohang to review.