fix: add Rule.event field to comply with json-rule-engine schema

[nurulhudaapon]

We are using json-rule-engine in our frontend, while json-rule-engine supports the Rule.event field with some for advance event handling feature, here in event we can add data in Rule.event.params but since python-rule-engine doesn't have that field instead has Rule.extra. To keep using json-rule-engine and python-rule-engine we need this field.

[nurulhudaapon]

Hi @santalvarez if you agree with the following then would love to get this merged and released sooner. Thanks!

[santalvarez]

Hey Im sorry about the delay I was on vacation. I will review this now