Indented code blocks aren't parsed into cells

[jlewi]

Here's a sample with indented code blocks
sample.txt

These are not parsed into code block cells.

There's two ways to potentially look at this

1. Markdown -> Notebook should always convert indented code blocks to cells
2. The AI prompt should not respond with indented code blocks

Part of the issue here is that if we are relying on markdown to convert into a numbered lists; I don't think the numbering will carry across cells in a notebook.

Related to #52