async addPage (options) {
    options.permalinkPattern = this.siteConfig.permalink
    options.extractHeaders = this.siteConfig.markdown && this.siteConfig.markdown.extractHeaders
    const page = new Page(options, this)
    await page.process({
      markdown: this.markdown,
      computed: new this.ClientComputedMixinConstructor(),
      enhancers: this.pluginAPI.getOption('extendPageData').items
    })
    const index = this.pages.findIndex(({ path }) => path === page.path)
    if (index >= 0) {
      // Override a page if corresponding path already exists
      logger.warn(`Override existing page ${chalk.yellow(page.path)}.`)
      this.pages.splice(index, 1, page)
    } else {
      this.pages.push(page)
    }
  }
Add a page

@returns {Promise<void>}
@api public