SEO Add Table of content for flatpages

[dtrucs]

Text summarization is a technique that involves condensing a longer piece of text into a shorter, more concise version while still retaining the most important information. With concise sentences, it allows search engine to determine what the page is about.

Proposal:

• create a boolean parameter enableFlatpageSummarization to global.json (set to false by default)
• add an id attribute to all <hn> tags from the page with a slugify of its textContent .
• extract all <hn> content from the current flatpage to create the table of contents, and link the anchors to the <hn>.