Export to markdown file that includes YAML metadata

Exporting events from the Narrative or Outline views to markdown files would be useful since many authors work with Obsidian (and other such apps).

Obsidian makes good use of YAML metadata, for example, by displaying it in tables via plugins such as Dataview and its in-development successor, Datacore. Thus, it would be useful if we could optionally include the YAML metadata for each event. Ideally, the user could select which YAML key-value pairs would be included, perhaps something like how the AT3/Obsidian sync setup works now.