[feature-request] support different line cap style (especially round-end)

[SteveKChiu]

First thanks for your great work. I notice rvg does not support different line cap style, it seems it is a common feature for vector drawing library. It would be great if the rvg::Shape can support round line cap style for non-looped path line.

[nyorain]

I agree, line caps, corner beveling and all these standard vector graphics features are on my todo list, it will be implemented in the more abstract shape-baking library katachi. As the feature is not very high up in the list though (and I don't got much time to work on this rn), don't expect this in the near future. Always open for PRs though :)