fill out readme

README.md

@@ -4,3 +4,36 @@ Template to get started with WebGPU C++ projects targetting
 WebAssembly via Emscripten. Easily build apps and then test
 and deploy with Webpack.
 
+## Building
+
+The C++ code is compiled with [Emscripten](https://emscripten.org/) to
+WebAssembly, and uses [CMake](https://cmake.org/) for build configuration.
+Both need to be installed and in your path to build the project.
+You can then run from the repo root directory:
+
+```
+mkdir cmake-build
+cd cmake-build
+emcmake cmake ..
+cmake --build .
+```
+
+This will build the C++ code with Emscripten to produce the WebAssembly
+build of the C++ code, and JavaScript files to import the Wasm into an app
+and from a worker thread. The build command will also copy these files into
+`./web/src/cpp/` to be used by the web app.
+
+## Running
+
+The app is a small TypeScript shim that sets up the WebGPU device
+and calls into the Wasm module to run `main` to start the app.
+After building the C++ code, you can run the app:
+
+```
+cd web
+npm i
+npm run serve
+```
+
+You can then visit `localhost:8080` in the browser to see the app running.
+

web/src/index.ts

@@ -1,5 +1,4 @@
 import WGPUApp from "./cpp/wgpu_app.js";
-//import wasm from "./cpp/wgpu_app.wasm";
 
 function sharedArrayBufferSupport()
 {