function is_block(node) {
	return (
		node.type === 'IfBlock' ||
		node.type === 'EachBlock' ||
		node.type === 'AwaitBlock' ||
		node.type === 'KeyBlock' ||
		node.type === 'SlotElement'
	);
}
@param {Compiler.AST.SvelteNode} node
@returns {node is Compiler.AST.IfBlock | Compiler.AST.EachBlock | Compiler.AST.AwaitBlock | Compiler.AST.KeyBlock | Compiler.AST.SlotElement}