function is_expression_attribute(attribute) {
	return (
		(attribute.value !== true && !Array.isArray(attribute.value)) ||
		(Array.isArray(attribute.value) &&
			attribute.value.length === 1 &&
			attribute.value[0].type === 'ExpressionTag')
	);
}
Returns true if the attribute contains a single expression node.
In Svelte 5, this also includes a single expression node wrapped in an array.
TODO change that in a future version
@param {AST.Attribute} attribute
@returns {attribute is AST.Attribute & { value: [AST.ExpressionTag] | AST.ExpressionTag }}