[Analyzer] Add LSP dart.analysisExcludedFolders to readme
[Analyzer] Add LSP dart.analysisExcludedFolders to readme

Change-Id: Iaa4cf8f9f2697c6fd3583018566f9201820ead8b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/173966
Auto-Submit: Danny Tuppeny <df4bf92e16bbb7396c50d637f6b7ad9a4c8c274c@tuppeny.com>
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk