Add a welcome screen - Githubissues

An initial implementation of the figma prototype. Actual functionality (like creating a new server) will be added in a separate PR

Things to consider:

is it responsive enough? I had to increase the initial window size to fit all of the content
should it appear only after logging in for the first time?
are all the texts set in stone? ("Get some help!" sounds funny)

Roller23 / Raino