[Feature Request] Allow caching parser results

[desttinghim]

I want to store the output of the tvg parser so that I can re-render without having to also re-parse the file. The primary benefit would be eliminating the need for an allocator at render time. With the way the current parser works, this is not very easy to do. My workaround in my current project was to record the memory usage after every iteration and then allocate a buffer of that size, rounded to the next multiple of 16.