addEntries(entries = {}) {
        if (typeof entries !== 'object') {
            throw new Error('Argument 1 to addEntries() must be an object.');
        }

        Object.entries(entries).forEach((entry) => this.addEntry(entry[0], entry[1]));
    }
Provide a has of entries at once, as an alternative to calling `addEntry` several times.

@param {Record<string, string|string[]>} entries
@returns {void}