Introduce ability to remove leading indents in a multiline string after a newline.

In dart if I create a multiline string like this:
```dart
String itemList = """
1. Item A
2. Item B
3. Item C
""";
```

I expect the output of `print(itemList)` to be as:
```
1. Item A
2. Item B
3. Item C
```

But the actual output comes out to be:
```
1. Item A
2. Item B
3. Item C
```

It would be helpful to introduce a method called `itemList.trimLeadingIndents()` that would give us the output as expected after removing the indents after every newline character.

I would like to contribute fixing this issue and providing a method but before that if the community can approve if they would like to have such method in the `Dart` language.

Any help would be appreciable.