Support multiple levels of sticky headers

[JordanLongstaff]

My company has a use case where we want to show multiple levels of sticky headers, e.g.:

Header A
---------------
  Header B <- sticks underneath Header A
  --------------
    ... <- some non-header items
  --------------
  Header C <- replaces Header B
  --------------
    ...
---------------
Header D <- replaces Header A and Header C
---------------
  ...

[goncalossilva]

Thanks for the request! We don't have this requirement internally, so it may be difficult for us to get to this in a timely manner. Assuming it can be done this without significantly increasing complexity, PRs are welcome! 🙂