pick canonical assets and colors for common elements like w3 logo and background

[olizilla]

The sign-in-up example requires the user to open a second window on access.web3.storage which has similar but different colours and logos. This is an early warning of the challenges of keeping the design of a bunch of web apps in sync.

we went for a light touch approach for ipfs-webui and captured our colours and fonts in a atomic style css lib over in https://github.com/ipfs-shipyard/ipfs-css which worked pretty well... folks could easily opt-in to consistency without having being forced to adopt any specific css framework.

[jchris]

@meghansinnott you have an asset library also