Warn about floating comments

[mhwelander]

Floating comments are removed when you introspect:

model User {

// I float!

}

Would be good to have a warning in VS Code so that users aren't confused when certain comments disappear.

[matthewmueller]

This feels like a bandaid to me. My preference would be to fix the AST with a specific Comment node for floating comments.

Free-floating comments are useful for documenting what the datamodel does or who's the primary owner of the datamodel.

// This datamodel powers our recommendation engine.
// 
// Owners: 
//   Mark <mark@prisma.io>
//   Alice <alice@prisma.io>
//   Nicole <nicole@prisma.io>

model User {

}

Since our Schema language is rather simple, we'd need Comment nodes in only two places: outside the blocks and inside.