Add `use` and not pollute namespace

Add use:

Syntax
```rust
use library.someClass.someFunction;
use library.someFunction;
use library.someVariable;

// Multiple use’s
use library.{someClass, someVar, someFunc};
```

Update grab to not pollute:

```dart
grab("somelib");

// To access the function
somelib.someFunc();
```

This is tbh p easy so this can be marked as a good first issue! :)