fix(xml): add missing 's' to '#instructions' in clone/doc

[lowlighter]

While taking a look at #96, noticed that doc and clone method referenced #instruction but it is actual defined as plural #instructions in the code

libs/xml/parse.ts

Lines 172 to 176 in 2969d11

	// XML processing instruction
	case Token.XMLInstruction: {
	const [name, ...raw] = value.split(" ")
	const instruction = Object.assign(xml_node(name, { parent: xml }), xml_attributes(raw.join(" ")))
	xml["#instructions"] ??= {}