/// Returns a CSS variable with a fallback if provided.
///
/// @param {String} $name - The variable name.
/// @param {Any} $var - The fallback value.
/// @return {String} - The CSS variable.
@function var-if($name, $var) {
	@if $var {
		@return var(--#{$name}, #{$var});
	} @else {
		@return var(--#{$name});
	}
}