Expose "getNewLineCharacter" function

<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Please read the FAQ first, especially the "Common Feature Requests" section. --> ## Suggestion Make `ts.getNewLineCharacter` public <!-- A summary of what you'd like to see added or changed --> ## Use Cases This is useful if developers create their own `FormatDiagnosticsHost`, but don't want to implement the logic to determine the `newLine` string based on the `newLine` compiler option. <!-- What do you want to use this for? What shortcomings exist with current approaches? --> ## Examples ```ts const formatHost: ts.FormatDiagnosticsHost = { getCurrentDirectory: () => projectDir || ts.sys.getCurrentDirectory(), getCanonicalFileName: fileName => fileName, getNewLine: () => ts.getNewLineCharacter(formatOptions) }; ``` <!-- Show how this would be used and what the behavior would be -->