Initial WASM implementation

[tychedelia]

Partially addresses #26.

Adds a new processing_wasm crate that operates similar toprocessing_ffi, i.e. wrap in a WASM/JS compat function.

We're helped by running in a single thread on desktop already, but on web we can't ever block the main thread, so we need a few additional non-blocking flavors of some methods that currently block on desktop.

We're generating JS bindings here because it's helpful to test. Most implementers will likely just bind directly to the WASM module.

Adds a justfile to help coordinate some of this. If you're not familiar, just is a common task running in the Rust ecosystem that's like a simplified make.

[tychedelia]

Somehow evidently I screwed this up again relative to ProcessingProjection.

[catilac]

getting this error when building:

error[E0428]: the name `image_load` is defined multiple times
   --> crates/processing_render/src/lib.rs:639:1
    |
633 | pub fn image_load(path: &str) -> Result<Entity> {
    | ----------------------------------------------- previous definition of the value `image_load` here
...
639 | pub async fn image_load(path: &str) -> Result<Entity> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `image_load` redefined here
    ```
    
    

[catilac]

getting this error when building:

error[E0428]: the name `image_load` is defined multiple times
   --> crates/processing_render/src/lib.rs:639:1
    |
633 | pub fn image_load(path: &str) -> Result<Entity> {
    | ----------------------------------------------- previous definition of the value `image_load` here
...
639 | pub async fn image_load(path: &str) -> Result<Entity> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `image_load` redefined here
    ```
    
    

I added a #[cfg(not target_arch = "wasm32")] to fn image_load(...) {} to test!

[catilac]

just seems to install wasm-bindgen and runs wasm-opt for both wasm-build and wasm-serve

[catilac]

This just needs the #[cfg(not...)] to compile but g2g!