Supporting empty block for spacing

[MarcARoberge]

Hi,

I tried to add empty blocks into a page and when it's converting, it's ignoring it. I tried to activate the breaks option from marked without sucess. Maybe du since the text array from the content is empty?

[nartc]

Do you know what an empty block could mean in terms of Notion API? like a ParagraphBlock would have Block#type === 'paragraph'

[MarcARoberge]

This is what I am getting

{
    "object": "block",
    "id": "",
    "created_time": "2021-10-27T21:17:00.000Z",
    "last_edited_time": "2021-10-27T21:17:00.000Z",
    "has_children": false,
    "archived": false,
    "type": "paragraph",
    "paragraph": {
      "text": []
    }
  },

[nartc]

I think it's related to this PR (markedjs/marked#363) from marked. They trim all non-breaking space between markdown blocks.

ParagraphBlock with empty text: [] should be parsed to: \n\n (https://github.com/nartc/notion-stuff/blob/main/libs/blocks-markdown-parser/src/lib/blocks-markdown-parser.ts#L152). However, due to the issue mentioned above, it just gets removed.

There are a couple of workarounds in the linked issue (eg: customizing a lexer) to handle this. Or if you'd like and if you think it makes sense, I'm welcoming PR to support this from blocks-markdown-parser.

Basically for the PR, I'd like to see:

• MarkdownParser accepts a new option: emptyParagraphToNonBreakingSpace (I mean you can come up with a better name if you'd like 😅)
• Based on this new option, and if paragraph.text is an [], then return   instead.