New Design -dialog changes with support Lit/TS

[Peppe]

• You should be able to choose if you create TS/Lit or (JS/P3 or HTML/P2) in Designer.
• You should be able to choose if the template will have a shadow root or if everything is in light dom.
• First time you use it it should default to TS/Lit and Light DOM. It should remember the selection from the last time and suggest the same for the next time you create a design.
• Creating a companion file should be changed to default on and it should remember the option as well.

[tanbt]

shadow/light dom thread: https://vaadin.slack.com/archives/C3XABCQGK/p1600246088309300