Describe the bug
Previously, escaped characters within strings were highlighted in a different color (I believe light yellow), to make them more obvious. But after activating LSP this doesn't seem to happen anymore.

To Reproduce

final str = 'this string \nhas an escaped character in it';

Expected behavior
Escaped characters should be more visible.

Screenshots

Versions (please complete the following information):

• VS Code version:

1.57.0-insider
Commit: b95b73b7b074f5dddccd57e5e290617f1a767ec1

• Dart extension version: 3.22.0
• Dart/Flutter SDK version:

Flutter 2.3.0-0.1.pre • channel unknown • unknown source
Framework • revision d72bfb8d07 (12 days ago) • 2021-04-26 06:05:55 -0700
Engine • revision de6e1adf97
Tools • Dart 2.14.0 (build 2.14.0-18.0.dev)