[Feature Request] Support for dynamic textStyle per partType

[githistory]

It'd be great to support dynamic textStyle per partType, allowing user to define styles based on part data.

My proposal would be to make partTypes' textStyle property accept function too. If a function is passed in, the library should call the function passing in part data, and use the return value of the function as the textStyle for the part.

Happy to send in a PR if we agree on the approach @dabakovich.