Add wasm example to manual (#3353)

std/manual.md

@@ -951,6 +951,33 @@ for await (const req of serve(":8000")) {
 $ deno run --importmap=import_map.json hello_server.ts
 ```
 
+## WASM support
+
+Deno can execute [wasm](https://webassembly.org/) binaries.
+
+<!-- prettier-ignore-start -->
+```js
+const wasmCode = new Uint8Array([
+  0, 97, 115, 109, 1, 0, 0, 0, 1, 133, 128, 128, 128, 0, 1, 96, 0, 1, 127,
+  3, 130, 128, 128, 128, 0, 1, 0, 4, 132, 128, 128, 128, 0, 1, 112, 0, 0,
+  5, 131, 128, 128, 128, 0, 1, 0, 1, 6, 129, 128, 128, 128, 0, 0, 7, 145,
+  128, 128, 128, 0, 2, 6, 109, 101, 109, 111, 114, 121, 2, 0, 4, 109, 97,
+  105, 110, 0, 0, 10, 138, 128, 128, 128, 0, 1, 132, 128, 128, 128, 0, 0,
+  65, 42, 11
+]);
+const wasmModule = new WebAssembly.Module(wasmCode);
+const wasmInstance = new WebAssembly.Instance(wasmModule);
+console.log(wasmInstance.exports.main().toString());
+```
+<!-- prettier-ignore-end -->
+
+WASM files can also be loaded using imports:
+
+```ts
+import { fib } from "./fib.wasm";
+console.log(fib(20));
+```
+
 ## Program lifecycle
 
 Deno supports browser compatible lifecycle events: `load` and `unload`. You can