Add support to combine different kind of Charts

[b3t4m1n]

or is it already possible.

btw. I love the charts!

[dautovicharis]

@b3t4m1n Thanks a lot for the support! I was too busy the last two months to contribute to Charts. However, I have a lot of changes locally regarding Multi-Platform support. I will try to push this ASAP because it is a top priority for now.

After that, I'll work on other open issues, including this one. Could you please give me one example of combined charts, and you can add more details?

Thanks!

[b3t4m1n]

like combining the Line Chart and Bar Chart (Stacked or Grouped)