Add c3_chart_fn.width() and c3_chart_fn.height() methods to chart API

I have to display a set of horisontal stacked bar charts on a single page. The requirement is that bars should have fixed width and the distance between bars also should be fixed. But the chart height should be automatically based on a number of categories.
bar.width.ratio bar.width does not help because cannot be used together and anyway the height is fixed.
Is there any way to automatically cahnge chart height based on the number of categories and keep bars and distance between them fixed?
Thnanks!

Start at the chart API and inspect the existing bar.width and bar.width.ratio options, then reproduce a horizontal stacked-bar chart with multiple categories. Done means chart.width and chart.height methods exist and the chart height can follow the category count while bar width and spacing remain fixed.

Written by the indexing model from the issue text.