ci: add deploy workflow + build script

build.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -eux
+
+cargo build --target=wasm32-unknown-emscripten --release
+
+mkdir -p dist
+
+cp target/wasm32-unknown-emscripten/release/rust_sdl2_wasm.wasm dist
+cp target/wasm32-unknown-emscripten/release/rust-sdl2-wasm.js dist
+cp index.html dist