bump winit to 0.20.0-alpha4

Author: antonok-edm

examples/Cargo.toml

@@ -37,7 +37,7 @@ gfx-backend-empty = { path = "../src/backend/empty", version = "0.3" }
 env_logger = "0.6"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-winit = "0.20.0-alpha3"
+winit = "0.20.0-alpha4"
 glsl-to-spirv = "0.1.4"
 
 [dependencies.gfx-backend-gl]