docs: update README with build instructions and requirements

README.md

@@ -1,9 +1,39 @@
 # totp-wasm-zig
 
 [![License](https://img.shields.io/github/license/gizmo-ds/totp-wasm-zig?style=flat-square)](./LICENSE)
+[![CI](https://img.shields.io/github/actions/workflow/status/gizmo-ds/totp-wasm-zig/testing.yml?branch=main&label=docker%20image&style=flat-square)](https://github.com/gizmo-ds/totp-wasm-zig/actions/workflows/testing.yml)
 
 > **Warning**  
-> This project is still in the early stage of development, and is not ready for production use.
+> This project is still in the early stage of development and is not ready for production use.
+
+# Requirements
+
+- [Zig](https://ziglang.org/)
+- [Binaryen](https://github.com/WebAssembly/binaryen) (Optional but recommended)
+- [Node.js](https://nodejs.org) (Optional)
+
+# Build
+
+## Compiling WebAssembly
+
+To reduce the size of the `.wasm` file, you can choose to install [Binaryen](https://github.com/WebAssembly/binaryen).
+
+[How to install Binaryen?](#how-to-install-binaryen)
+
+```fish
+zig build
+zig build bind
+```
+
+## Packaging the totp-wasm JavaScript bundle
+
+```fish
+npx esbuild packages/totp-wasm/index.ts --bundle --format=esm --platform=node --target=es2017 --minify --outfile=packages/totp-wasm/index.js
+```
+
+# How to install Binaryen?
+
+You can download the latest release of Binaryen from [https://github.com/WebAssembly/binaryen/releases](https://github.com/WebAssembly/binaryen/releases). Once that's done, simply extract the compressed file somewhere. `wasm-opt` will be in the `bin` folder.
 
 ## License