[Feat] keep empty line after HashBang

[Airkro]

Is your feature request related to a problem?
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Currently, this plugin will remove empty line after HashBang.

  #!/usr/bin/env node
-                               
  import foo from 'bar';

Describe the solution you'd like
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• Keep an empty line after HashBang, if it exists.

Describe alternatives you've considered
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• Enforce an empty line after HashBang.

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[fbartho]

I personally don’t see a problem with this feature change.

I think we already have a special case for shebang-lines, so it’s probably a small tweak to adjust this code.

The biggest problem is deciding if this is a breaking change from a versioning perspective.

[IanVS]

I think it could be considered a "bugfix", though we might want to release in a minor. Even prettier itself allows formatting changes between versions. We should make our stance explicit in the README, though...

[Airkro]

Add a new option to enable that feature, can avoid breaking change.

[IanVS]

Yes, but that's how we ended up with a bajillion options previously, and we worked hard to remove them. Prettier itself is opinionated and has very few options, and we want to follow that same philosophy.