fix: test infra for WASM

[schell]

This adds proper test infrastructure for WASM tests (through wasm-bindgen-test).

• adds an axum server to supply tests with static files from test_img, as well as the ability to diff images and save to the filesystem.
• adds an xtask command and cargo alias, xtask test-wasm to run WASM tests
• removes futures_lite, except from tests, as calling futures_lite::future::block_on on web panics
• changes Context API to be async
• reading images from GPU is now async
• changes the example-wasm to load the fox glb, helipad hdr skybox and have some UI (still needs tweaking which will happen in a follow-up PR)
• fixes a bug where naga was flipping the y axis on all vertex shaders
• adds tutorial shaders for progressive WASM tests
• adds WASM tests
• fixes a bug where SPIR-V shaders would not transpile to WGSL when renderling is built outside of its repo workspace
• adds WASM tests to github workflows I spent way too much time thrashing against CI trying to provision a browser on Ubuntu that will run the tests. It's local only for now.

Fixes #196.