add readme

README.md

@@ -0,0 +1,17 @@
+How to build the wasm module:
+```
+cd wasm-module
+wasm-pack build --target web --out-dir pkg
+```
+
+How to serve the web demo (requires wasm module):
+```
+cd web-demo
+python3 -m http.server
+```
+
+How to run the native player:
+```
+cd native-player
+cargo run --release
+```