Glob or RegExp import/export

### Usage
In some situation, we need to export (sometimes import) multiple files, and the whole of them are located in the same directory

### Syntax
we can import/export with glob or RegExp syntax. With this feature, we don't need to export like this or creating multiple mini-libraries:
```dart
library my_lib;

export 'src/core/buttons/text_button.dart';
export 'src/core/buttons/image_button.dart';
// and so on...
```
instead, we can use it like:
```dart
library my_lib;

export 'src/core/buttons/*_button.dart';
```

I'll happy with your ideas and comments =)

No files, tests, or implementation entry points are named. Start by reading the proposed glob or RegExp import/export syntax and the comment thread; done would require an agreed language design and a documented path to implementation.

Written by the indexing model from the issue text.