Fix with-webassembly example and convert to Typescript

[maxproske]

• Fixes with-webassembly example unable to build with the current next.config.js. Rust WebAssembly module in an ES module wrapper from wasm-pack fails to load in Next.js #29362 (comment)
• Converted example to TypeScript

// Before
config.output.webassemblyModuleFilename = 'static/wasm/[modulehash].wasm'

// After
config.output.webassemblyModuleFilename =
  isServer && !dev
    ? '../static/wasm/[modulehash].wasm'
    : 'static/wasm/[modulehash].wasm'

> Build error occurred
Error: Export encountered errors on following paths:
        /
    at /Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/export/index.js:408:19
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Span.traceAsyncFn (/Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/trace/trace.js:79:20)
    at async /Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/build/index.js:1342:21
    at async Span.traceAsyncFn (/Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/trace/trace.js:79:20)
    at async /Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/build/index.js:1202:17
    at async Span.traceAsyncFn (/Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/trace/trace.js:79:20)
    at async Object.build [as default] (/Users/max/dev/next.js/examples/with-webassembly/node_modules/next/dist/build/index.js:65:29)
 ELIFECYCLE  Command failed with exit code 1.

Documentation / Examples

• Make sure the linting passes by running pnpm build && pnpm lint
• The "examples guidelines" are followed from our contributing doc

[maxproske]

Suggested change

	const module$ = WebAssembly.instantiate(addWasm)
	export default async function handler() {
	const instance = (await module$) as any
	export default async function handler() {
	const instance = (await WebAssembly.instantiate(addWasm)) as any

I'm not aware what the advantage of initiating the wasm module$ outside the API handler like this is. But I've left it as-is, unless you want to commit this suggestion.

[ijjk]

Instantiating outside of the handler allows re-using the same instance which is a bit more performant so I think it's good we leave that as is.