feat/chunking_by_title_tokens

[erik-squared]

would it make sense for there to be a version of chunk_by_title() that operates on tokens rather than characters? using the same soft window and small chunk combining logic, except using tokens rather than characters.

i see that there is also a chunk_by_attention_window() that's part of the staging/destination side of things, so it seems like one could use the 2 in succession.