Building CanvasKit uses very similar logic to PathKit, so there
was a fair amount of copy/paste/customize.
Fixes the name of skia.js/wasm -> canvaskit.js/wasm and
adds a package.json to formally track versions.
Also move PathKit helper scripts to align better.
Docs-Preview: https://skia.org/?cl=160463
Bug: skia:
Change-Id: Ie75b30592dcc4d520dca41f6f5579006aaa8849b
Reviewed-on: https://skia-review.googlesource.com/c/160463
Reviewed-by: Eric Boren <borenet@google.com>
8e9750d3c5