☂ Add section for Flutter for Web Developers

[vsmenon]

What information is missing?

Content targeted to Web developers interested in Flutter and Flutter for the Web in particular. Might cover text selection, links, etc., in particular.

How would you like us to fix this problem?

A guide akin to the ones we have here: https://docs.flutter.dev/#docs for SwiftUI, Android, etc.

[atsansone]

@RedBrogdon : Could we contract for this?