Add FAQ for redrawing after other output

[joshka]

https://discord.com/channels/1070692720437383208/1072907135664529508/1227559342077775892

In sync code, is it possible to somehow trigger a full redraw of everything. I'm restoring, launching external command and then initializing the TUI again.. It kinda works but only draws when I do something that changes something

Got it by running terminal.clear() before drawing

FAQ should be a smaller question. Answer should expand on why this is necessary (terminal double buffering) and link to the concepts page that explains this in detail. https://ratatui.rs/concepts/rendering/under-the-hood/