Similar to how the analysis server will provide color previews to editors, it would be nice if icon paths for previews could also be provided.

Right now Dart-Code ships a full copy of the Flutter's Material/Cupertino icons in the extension and adds gutter icons based on text names. This doesn't scale very well to third party packages, needs duplicating in each editor using the LSP server, and doesn't version with the package/SDKs (all users get the same icon previews regardless of their version). It also makes the extension quite large (right now, ~99% of the Dart-Code extension file is icon previews).

@stevemessick has done some work on generating the previews from a font file in IntelliJ (flutter/flutter-intellij#5504, flutter/flutter-intellij#5595) but it has better access to things like ASTs than LSP-based editors so it would be better implemented in the server for those.