Set library & settings through URL [Feature]

For example:

```js
https://codepan.js.org/#/?npm=react&format=html,css
```

Initialize with the react package from npm and display just the html & css panels.

BTW nice work on this 👍

Start by tracing how the application reads the URL hash, initializes an npm package such as react, and controls visible panels. Confirm the expected behavior for the example URL, including package initialization and showing only the html and css panels; done means the URL reproduces that state on load.

Written by the indexing model from the issue text.