Fix folding of cells

[wadethestealth]

Closes #1508

[aviatesk]

@wadethestealth
Thanks for addressing this issue ! Your fix works.

As a further fix, I wonder you feel like you can fix this too ?
fold-current-cell for multiple grammar files (like markdown) can fold multiple cells if invoked on header of cell. Please refer to the example below:

Before folding:

After folding (dispatch on ```python):

[wadethestealth]

@aviatesk Currently this is impossible. We currently detect for embedded scopes, which the header is not apart of. The other way to detect would be a markdown code block, but this is specific to markdown and if two code blocks have no blank line between them they will read as the same block. So for now its worth noting that the header is not a part of the cell

[aviatesk]

@wadethestealth
Oh so if I dispatch fold-current-cell on an header, the detected scope would be just an grammar of the body text (like markdown, pweave markdown or so) ?

Then I wonder we should disable the command on a body text of multi-grammar files including header.

[wadethestealth]

Correct.

Also, You are totally right since markdown isn't considered a cell but more of a wrapper @aviatesk

[aviatesk]

@wadethestealth
Okay. Anyway, let's put this to another PR/issue.