Incorrect structure for blockquotes

[garyThrels]

The blockquote structure results in a 2D array instead of a single layer array in the content

{
        "type": "blockquote",
        "content": [
            {
                "type": "paragraph",
                "content": [
                    [
                        {
                            "type": "text",
                            "text": "Initial Setup",
                            "marks": []
                        }
                    ]
                ]
            }
        ]
    },

[garyThrels]

I can try and check this out later myself if that is ok

[CharlieGreenman]

@garyThrels sure feel free to make a pull request with proper unit testing and i'll approve/merge

[garyThrels]

I converted the function to be recursive, this way it can be properly reused to handle the blockquote internals.

I also confirmed the test expectations are in a correct format by comparing them in Atlassian's playground, with only difference being they would not have an empty marks: [] array, but kept it there since its not a breaking difference.

#20