addHeading(text, level) {
        const tag = `h${level}`;
        const allowedTag = ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'].includes(tag)
            ? tag
            : 'h1';
        const element = this.wrap(allowedTag, text);
        return this.addRaw(element).addEOL();
    }
Adds an HTML section heading element

@param {string} text heading text
@param {number | string} [level=1] (optional) the heading level, default: 1

@returns {Summary} summary instance