Missing format_to overload using a style.

[davidchisnall]

There is no overload of format_to that takes a style argument, so if you wish to use a style for a custom formatter then you must first use format to generate a string and then copy the output to the iterator.

[vitaut]

Should be easy to add. PRs are welcome =).

[vitaut]

Closing due to inactivity and since styles are primarily for console output.