Markdown: fix several issues with lists and continuations

Importer fixes:
- the first list item after a heading doesn't keep the heading font
- the first text fragment after a bullet is the bullet text, not a
  separate paragraph
- detect continuation lines and append to the list item text
- detect continuation paragraphs and indent them properly
- indent nested list items properly
- add a test for QTextMarkdownImporter
Writer fixes:
- after bullet items, continuation lines and paragraphs are indented
- indentation of continuations isn't affected by checkboxes
- add extra newlines between list items in "loose" lists
- avoid writing triple newlines
- enhance the test for QTextMarkdownWriter

Change-Id: Ib1dda514832f6dc0cdad177aa9a423a7038ac8c6
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

0 files changed, 0 insertions, 0 deletions