SEO audit tool

A common task is to crawl a site, analyzing page content, meta tags, etc. It would be a nice time-saving feature to have the CMS perform this analysis and produce an interactive, or downloadable report.

My initial thoughts are that this could be broken into a few categories. Search and Social.
* **Search** would report on titles, descriptions, word count of page, structured data, redirects pointing to that page, etc.
* **Social** would check for opengraph and twitter settings, and maybe render a preview of what that would look like

This feature could potentially live in the SEO settings panel. Additionally, we could potentially add some of this of the SEO tab on each page, similar to what Yoast does for WordPress.

No files, tests, or entry points are named. Start by reviewing the SEO settings panel and the per-page SEO tab mentioned in the issue, then define the scope of the Search and Social checks and report format. Done should mean the CMS can crawl a site and produce the agreed interactive or downloadable audit report.

索引モデルが issue の本文から書いたものです。