Add support for separator option

[smarth55]

This adds support for the separator option that is used with concat-with-sourcemaps. A separator arg is passed if given, \n will be used as a default if no separator is provided.

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[GitCop]

There were the following issues with your Pull Request

• Commit: 37f9070
• Commits must be in the following format: %{type}(?%?{scope})?: %{description}

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[GitCop]

There were the following issues with your Pull Request

• Commit: 37f9070

• Commits must be in the following format: %{type}(?%?{scope})?: %{description}

• Commit: 14ba4e5

• Commits must be in the following format: %{type}(?%?{scope})?: %{description}

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There were the following issues with your Pull Request

• Commit: 37f9070

• Commits must be in the following format: %{type}(?%?{scope})?: %{description}

• Commit: 14ba4e5

• Commits must be in the following format: %{type}(?%?{scope})?: %{description}

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[markstos]

I'm curious about a response from humans about this proposal . The goal was to have an option to add an explicit character between files if desired, like a semicolon for joining JavaScript files.