Provide more usage examples (e.g. searching for fields)

[mwllgr]

Hi,

first off: Nice package! I just spent a good half an hour looking for suitable packages and yours is the first one that looks really promising to me, especially because it has some nice validation features! 👍🏻

I think it would be a nice-to-have if you'd include more examples of working with the custom fields. For example, how would I search for models that have a certain value in a custom field - do I just use normal Eloquent syntax?

Thanks! :)