Saving large Jupyter notebooks fails due to the string length restriction of JSON.stringify

[DonJayamanne]

Given we're serializing a lot of cells, we can easily serialize the cells one by one and then construct the bytes from that, instead of building a string.

I.e. notebook = {cells: [.....], metadata: {...}}

pseudo code:
json = [TextEncoder.encode({), ...notebook.cells.map(cell => TextEncoder.encode(JSON.stringify(cell)))];

Given that we know the indent level, its easy to construct the JSON string in pieces of bytes.

[DonJayamanne]

@rebornix /cc

[DonJayamanne]

This will address the issue, however we need a way to read the JSON as well,
However given that no one seems to be running into this issue (unable to save/load large notebooks), I'm changing this from bug to paper cut for now