Finding Layer in tree should not have to search for LAYER_NAME

[bartveneman]

This messes with my brain too much:

const ast = parse_atrule_prelude('import', params)

for (const node of ast) {
	if (node.type === LAYER_NAME && !node.name) {
		// LAYER_NAME???? 
	}
}

given layer(test) I expect: node.type === LAYER or node.type === FUNCTION and node.first_child.type === LAYER_NAME