Add the ability to automatically insert missing } and )

[josejmoran]

Describe the bug
If you change some code the beginning ( and { are easily traceable. But if there is a missing end ) or } it is a nightmare to find which one is the missing pair.

To Reproduce
Steps to reproduce the behavior:
Just copy some code from another part of your code and if there is a missing ) or } is hard to tell where and which is missing a ) or }

Expected behavior
Since you have all the beginning ( and { is it possible to kind of automatically match them and if there is one missing add it automatically.

Screenshots
If applicable, add screenshots to help explain your problem.

Versions (please complete the following information):

• VS Code version: 1.56.1
• Dart extension version:
• Dart/Flutter SDK version: 2.0.6