Add option to enasure newline at the end of any generated file

[pront]

💡 Feature description

Either add an option (e.g. a new cli argument) or change the default behavior of the tool to ensure a newline is added at the end of each generated file. This would be very helpful since many linting tools might report a missing newline at EOF as an error.

A common case where this is needed is described here: https://github.com/rustwasm/wasm-pack/issues/1161.

💻 Basic example

From:

*

To:

*
<-- newline added here