async renderPage (page) {
    const pagePath = decodeURIComponent(page.path)

    const context = {
      url: page.path,
      userHeadTags: this.userHeadTags,
      title: 'VuePress',
      lang: 'en',
      description: '',
      version
    }

    let html
    try {
      html = await this.renderer.renderToString(context)
    } catch (e) {
      console.error(logger.error(chalk.red(`Error rendering ${pagePath}:`), false))
      throw e
    }
    const filename = pagePath.replace(/\/$/, '/index.html').replace(/^\//, '')
    const filePath = path.resolve(this.outDir, filename)
    await fs.ensureDir(path.dirname(filePath))
    await fs.writeFile(filePath, html)
    return filePath
  }
Render page

@param {Page} page
@returns {Promise<string>}
@api private