Create a blank desktop app using Compose

[saket]

The current (work-in-progress) macOS app is built using SwiftUI, but setting up different source-sets for parsing markdown and syncing through git on the JVM and kotlin/native is proving to be a bit painful. Let's use Compose for building the desktop app instead: https://jetbrains.com/lp/compose.

My plan is to ramp up the Android app a bit by adding support for folders and archiving notes, and then get the desktop app up and running.