Convert this package to typescript

[armandabric]

This package is writted in Flow, and let's be honest, today it's not the more used static type checker.

To facilitate the maintenance of the package and avoid afraid new contributor let's convert it to TS.

[ghost]

Hello @armandabric could we work on this together

[francisashley]

I'd help with this.

[DanielHara]

@armandabric,
I'd like to help with this!
First, I'd like to ask for the status, and whether we already thought about a Roadmap for this. If not, I'm willing to supply a roadmap by breaking the task down into smaller steps, in order to make it happen.