Add flag to support using double-quoted strings if string contains single-quotes but no double-quotes

[nkiesel]

This will be easier to read, and is also the preferred quoting for TypeScript and many other formatting tools. This then should use single quotes as default, but would use "It's my birthday" instead of 'It\'s my birthday'.

[nkiesel]

If you want, I can file a PR for this

[nkiesel]

created PR