Experimental wgpu WebGL backend support

- Added missing `draw_cache_align_4x4` call for `brush_glyph` on wasm32 target
- Added WebGL support to `integratio_wgpu` example
- Fixed test.yml CI workflow
- Removed spir-v shader in `integration_wgpu`; Fixed formatting
- Removed redundant `BoxStream` typedef

examples/integration_wgpu/README.md

@@ -15,5 +15,22 @@ You can run it with `cargo run`:
 cargo run --package integration
 ```
 
+### How to run this example with WebGL backend
+NOTE: Currently, WebGL backend is is still experimental, so expect bugs.
+
+```sh
+# 0. Install prerequisites
+cargo install wasm-bindgen-cli https
+# 1. cd to the current folder
+# 2. Compile wasm module
+cargo build -p integration_wgpu --target wasm32-unknown-unknown
+# 3. Invoke wasm-bindgen
+wasm-bindgen ../../target/wasm32-unknown-unknown/debug/integration_wgpu.wasm --out-dir . --target web --no-typescript
+# 4. run http server
+http
+# 5. Open 127.0.0.1:8000 in browser
+```
+
+
 [`main`]: src/main.rs
 [`wgpu`]: https://github.com/gfx-rs/wgpu