(Metadata) Use the first highest-level heading as the document title

[OndraZizka]

Often, the page title is the same as the document top heading. In JBake, the title is used as the top heading. But from the editation point of view, it would be more user friendly if the title could be taken right from the document. Like below:

date: 2018-07-22
tags: feature-request
status: published

# The first highest-level title would be used for title of the page automatically

Some content

The title could be overriden using title:, just like it works now.

[jonbullock]

This is done for AsciiDoc content as the metadata header is optional but for Markdown, and I'm assuming your example is Markdown, need to check Flexmark allows interrogation of the content structure via some API first.