Path in the software renderer

[ogoffart]

The Path element is not supported with the software renderer.

We have different choice to implement it:

1. use some third party crate such as tiny_skia or something to draw the path in an cached image. The drawback is that this will require std, but should be fairly easy to implement.
2. Make it in a way that could work with no_std and with minimal allocation on MCUs

[tronical]

zeno might also be an option for implementing the path rendering. It's also used by swash and has this nice Scratch pattern to re-use heap allocations.