Better Overpass output format detection

[jacobwhall]

This is how I detect Overpass output format right now:

skyway/src/overpass.rs

Lines 21 to 33 in ff6a764

	let re = Regex::new(r"^out:[a-z]$").unwrap();
	let output_format = if query.contains("[out:xml]") {
	OverpassOutputFormat::Xml
	} else if query.contains("[out:json]") {
	OverpassOutputFormat::Json
	} else if re.is_match(&query) {
	return Err(SkywayError::InvalidInputFile(
	"Your Overpass query requests an output format that skyway cannot parse. Please request XML or JSON, if possible.".to_string(),
	));
	} else {
	OverpassOutputFormat::Xml
	};

I'd like to make this a little bit smarter, and avoid matching [out:xml] or [out:json] anywhere in the query outside of the first line(s). Shouldn't be too hard to implement regex for each of these that's aware of comments and semicolons.