Better first launch experience

It would be nice to make the welcome screen a bit more welcoming for new users :)

• Homeserver choice can be a drop down list of some popular options (matrix.org, kde.org, tchncs.de) + "Custom", which shows the input field
• Optional fields can be hidden in an "Advanced" press-to-expand section, to make the page look less overwhelming
• A small text intro / art at the top, maybe to explain the concept of the platform ("Welcome to Matrix!")

Hopefully VDG can help with this. Also Kaidan has something similar.