### Bug fixes

Block-level markup inside a heading is no longer escaped by the serializer.

Do not backslash-escape a `+` at the start of line when it isn't followed by a space. Upgrade to markdown-it 14

### New features

`MarkdownSerializerState.renderInline` now takes a parameter that controls whether block-level markup should be escaped.

Upgrade to markdown-it version 14, which provides ES modules.