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

wgpu/Cargo.toml

@@ -25,6 +25,7 @@ canvas = ["iced_graphics/canvas"]
 qr_code = ["iced_graphics/qr_code"]
 default_system_font = ["iced_graphics/font-source"]
 spirv = ["wgpu/spirv"]
+webgl = ["wgpu/webgl"]
 
 [dependencies]
 wgpu = "0.12"