Preserve whitespace while parsing

[Michael-F-Bryan]

At the moment, we deliberately filter out whitespace and comment tokens when constructing the Input for our Parser.

scad-rs/crates/syntax/src/parser.rs

Lines 156 to 166 in 558c141

	impl<'a> Input<'a> {
	fn new(tokens: impl IntoIterator<Item = (SyntaxKind, &'a str)>) -> Self {
	// FIXME: Blindly skipping whitespace and comments like this means
	// Rowan will never see them, so all our token spans will be wrong.
	let tokens = tokens
	.into_iter()
	.filter(|(k, _)| *k != SyntaxKind::WHITESPACE && *k != SyntaxKind::COMMENT)
	.collect();
	Input(tokens)
	}

Ideally, we would have a way to retain these tokens while making sure the parser never sees them, but a naive linear scan in Input::at() would have a massive impact on performance.