### Bug fixes

Make sure blank lines at the end of code blocks are properly serialized.

Convert soft breaks (single newlines) in Markdown to spaces, rather than newlines in the ProseMirror document, because newlines tend to behave awkwardly in the editor.

Fix a bug that cause the object passed as configuration to `MarkdownSerializer` to be mutated. Add release note

Include CommonJS type declarations in the package to please new TypeScript resolution settings.

### New features

A new option to `MarkdownSerializer` allows client code to configure which node type should be treated as hard breaks during mark serialization. Remove the extra left bracket