Add support for rendering raster images

[ivantishchenko]

Resolves #29. This extension allows us to render raster images alongside vector graphics.

This can be used to add support for rendering an <image> tag in SVG. An <image> tag contains embedded raster images. Some SVG describe vector geometric shapes on top of raster textures.
sammycage/lunasvg#113
sammycage/lunasvg#13

Here is an example image produced with plutovg_image. There are 4 different raster textures under the vector geometric shape of a face.

[sammycage]

Interesting! Looking forward to seeing this merge and the positive impact it brings to SVG rendering! 👏🚀

[ivantishchenko]

@sammycage Thank you for the feedback! What is the best way to proceed? Could this code be merged into the main branch of plutovg?

Afterwards, I would love to use it from lunasvg to finish the implementation of <image>. Should this code also be committed in one commit to the repository of lunasvg to patch its copy of plutovg? Alternatively, the repository lunasvg can use plutovg as a submodule. This way the changes will be applied to plutovg only and lunasvg would just reuse them.

https://github.com/sammycage/lunasvg/tree/master/3rdparty/plutovg

[sammycage]

Resolved in the latest version.