Redesign Start Page

[ShMcK]

Requirements:

• should contain the logo (see #425)
• should loosely explain the extension for someone unfamiliar
• should have Start/Continue buttons

The app uses https://fusion.design/, essentially an internal version of https://ant.design developed by Alibaba Design.

As it's easier to develop with component libraries, it may help to get a rough understanding of the Alibaba Design philosophy. Unless your Mandarin is alright (你会说中文吗?) - might be worth checking out https://ant.design/docs/spec/introduce over the fusion.design docs.

[jordanliu]

Update: Launched storybook and saw the current update, gonna use it as a base and make some experimental mockups