Some polishing

[alfonsogarciacaro]

I was trying to make the arguments of the event handlers typed but then I went through the whole api to try to avoid to avoid having untyped arguments in the public signatures. There are some small breaking changes, but hopefully it's ok if the package is still in beta (or at least before v1 release).

There are still things from the ReactFlow documentation that are not implemented. I will try to send more PRs as things come up :)

[tforkmann]

This is soo great! Thanks Alfonso!

Will release the new version soo.

Gonna try to publish the docs later this week.