Note: This should function the same as lex.LineHandler.currentIndexFormsLineEndingPair
pub fn formsLineEndingPair(source: []const u8, line_ending: u8, next_index: usize) bool
pub fn formsLineEndingPair(source: []const u8, line_ending: u8, next_index: usize) bool {
if (next_index >= source.len) return false;
const next_ending = source[next_index];
return utils.isLineEndingPair(line_ending, next_ending);
}