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

.github/workflows/test.yml

@@ -37,3 +37,5 @@ jobs:
       run: cargo build --package tour --target wasm32-unknown-unknown
     - name: Check compilation of `todos` example
       run: cargo build --package todos --target wasm32-unknown-unknown
+    - name: Check compilation of `integration_wgpu` example
+      run: cargo build --package integration_wgpu --target wasm32-unknown-unknown