add quick-start docs

docs/quick-start.md

@@ -0,0 +1,21 @@
+## Install
+
+```bash
+npm install webtorrent
+```
+
+## Quick Example
+
+```js
+var client = new WebTorrent()
+
+var torrentId = 'magnet:?xt=urn:btih:6a9759bffd5c0af65319979fb7832189f4f3c35d'
+
+client.add(torrentId, function (torrent) {
+  // Torrents can contain many files. Let's use the first.
+  var file = torrent.files[0]
+
+  // Display the file by adding it to the DOM. Supports video, audio, image, etc. files
+  file.appendTo('body')
+})
+```