Function leadingWs

lib/html/syntax.js:5143–5152

(
		/** @type {CharToken} */ t,
		/** @type {boolean} */ insert
	)

	// leading whitespace when `insert`, returns the non-whitespace remainder
	// token (or null when the token was entirely whitespace).
	const leadingWs = (
		/** @type {CharToken} */ t,
		/** @type {boolean} */ insert
	) => {
		const m = /^[\t\n\f\r ]+/.exec(t.data);
		const ws = m ? m[0] : "";
		if (ws && insert) insertCharacters(ws, t.start, t.start + ws.length);
		if (ws.length === t.data.length) return null;
		return { ...t, data: t.data.slice(ws.length), start: t.start + ws.length };
	};

	const isAllWs = (/** @type {string} */ s) => {
		for (let i = 0; i < s.length; i++) {