Fix strange behavior with list close tags and empty list tags

Fix the first two points in #61621.

Support for two  writing ways: compact or loose. The loose one is designed for easy editing in the editor.
For this, the first blank line (if exists) right after the list tags (`[ol]`, `[/ol]`, `[ul]`, and `[/ul]`)
will be ignored.

Make sure the empty list contains at least one item, that is, an empty list is ultimately a list with one item.
As a reminder here is a list.

0 files changed, 0 insertions, 0 deletions