Add SvelteKit Example (#684)

* Add SvelteKit Example

* package-lock.json

apps/sveltekit-app/src/lib/FFmpegDemo.svelte

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+<script lang="ts">
+	import { FFmpeg } from '@ffmpeg/ffmpeg';
+	// @ts-ignore
+	import type { LogEvent } from '@ffmpeg/ffmpeg/dist/esm/types';
+	import { fetchFile, toBlobURL } from '@ffmpeg/util';
+
+	let videoEl: HTMLVideoElement;
+
+	const baseURL = 'https://unpkg.com/@ffmpeg/core-mt@0.12.6/dist/esm';
+	const videoURL = 'https://raw.githubusercontent.com/ffmpegwasm/testdata/master/video-15s.avi';
+
+	let message = 'Click Start to Transcode';
+
+	async function transcode() {
+		const ffmpeg = new FFmpeg();
+		message = 'Loading ffmpeg-core.js';
+		ffmpeg.on('log', ({ message: msg }: LogEvent) => {
+			message = msg;
+			console.log(message);
+		});
+		await ffmpeg.load({
+			coreURL: await toBlobURL(`${baseURL}/ffmpeg-core.js`, 'text/javascript'),
+			wasmURL: await toBlobURL(`${baseURL}/ffmpeg-core.wasm`, 'application/wasm'),
+			workerURL: await toBlobURL(`${baseURL}/ffmpeg-core.worker.js`, 'text/javascript')
+		});
+		message = 'Start transcoding';
+		await ffmpeg.writeFile('test.avi', await fetchFile(videoURL));
+		await ffmpeg.exec(['-i', 'test.avi', 'test.mp4']);
+		message = 'Complete transcoding';
+		const data = await ffmpeg.readFile('test.mp4');
+		console.log('done');
+		videoEl.src = URL.createObjectURL(
+			new Blob([(data as Uint8Array).buffer], { type: 'video/mp4' })
+		);
+	}
+</script>
+
+<div>
+	<!-- svelte-ignore a11y-media-has-caption -->
+	<video bind:this={videoEl} controls />
+	<br />
+	<button on:click={transcode}>Start</button>
+	<p>{message}</p>
+</div>

apps/sveltekit-app/src/lib/index.ts

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+// place files you want to import through the `$lib` alias in this folder.