feat(doc): add readme to docs landing page

docs/src/introduction.md

@@ -1,3 +1,21 @@
 ![wasm ferris](https://rustwasm.github.io/wasm-pack/public/img/wasm-ferris.png)
 
 <h1 style="text-align: center;">Welcome to the <code>wasm-pack</code> docs!</h1>
+
+This tool seeks to be a one-stop shop for building and working with rust-
+generated WebAssembly that you would like to interop with JavaScript, in the
+browser or with Node.js. `wasm-pack` helps you build rust-generated
+WebAssembly packages that you could publish to the npm registry, or otherwise use
+alongside any javascript packages in workflows that you already use, such as [webpack]
+or [greenkeeper].
+
+[bundler-support]: https://github.com/rustwasm/team/blob/master/goals/bundler-integration.md#details
+[webpack]: https://webpack.js.org/
+[greenkeeper]: https://greenkeeper.io/
+
+This project is a part of the [rust-wasm] group. You can find more info by
+visiting that repo!
+
+[rust-wasm]: https://github.com/rustwasm/team
+
+![demo](https://github.com/rustwasm/wasm-pack/raw/master/demo.gif)