Optional notebook output with interleaved runtime and screenshots

[bmorris3]

Description

This is a rough PR with an additional option to output a copy of the source notebook with new markdown cells injected after each executed code cell. The new markdown cells show the last screenshot captured from the preceding code cell, the elapsed time between executing the code cell and the final update to the output, and the number of output updates captured before the cell was considered complete.

I spent some time investigating if it's possible to get the notebook file path via playwright, rather than asking for it as a command-line argument, but I haven't found a way yet. Any tips?

There's one small commit that changes the output path format a bit from proper ISO, since OS X doesn't like colons in file paths.

This was put together pretty quickly, so feel free to add comments or commits.