Release v1.3.5

Fixed GitLab issue #1: section parser misidentified indented overlines and :: as section adornments.

- Section adornments/titles/underlines must be flush-left.
- Standalone :: is no longer accepted as a section underline.
- Transitions must be flush-left.
- Paragraph parsing stops before standalone :: for literal-block handling.
- Indented blocks no longer generate sections from dedented whitespace.