Previously there was a limit of 256k pathtags in a scene, due to the need for multi-dispatch prefix sum for the pathtag monoid. This patch increases the limit to 64M, which ought to be enough for most applications.
It works by having 4 dispatches for the pathtag prefix sum: 2 to reduce, then 2 to scan.
* Move the vello crate to the root of the crate
* Add warning that README is work in progress
* Add newline in warning
* Move the unlicense into the shader folder
* Fixup wgsl-analyzer include paths