Add more data to frontmatter

[Edo78]

Adding more data to frontmatter:

• title
• chapter
• author

Adding even some metadata can be really useful:

• newly_imported (can be used to show the recently imported notes that should be managed)
• body_hash (to check if the note is still the same and can be updated, if updated on koreader, or if it was manually update)

Made the notes more useful because those data can be used by other plugin that can harness them (eg. dataview can be used to create list of notes of a chapter of a book or a list of all the notes about the books of a specific author)

[Edo78]

Instead of newly_imported I think yet_to_be_edited is more intuitive because a note can be imported a lot earlier but never edited so it's safe to reimport an updated version without losing anything