Chrome Web Store listing needs updating

[maxmilton]

Before we can publish a new version on the Chrome Web Store it's now required to have screenshots and privacy info. This would be a good opportunity to rewrite the content etc. too.

Related: #259

[maxmilton]

Added one image to the store listing however it's more of a placeholder since you must have at least one image to be able to publish. It's literally a screenshot of a fresh chrome instance + the extension.

We should definitely spend a little time to make some nice images showcasing the most interesting features.