docs: Add some recommendations on table partitioning

[jpsamaroo]

It's not entirely obvious to new users what value should be specified for chunksize, yet its choice is vital to getting good performance. It would be great if we could add to the docs some recommendations (and possibly examples) of how to choose a good chunksize value. Specifically, we could list a few basic recommendations:

• Specify it as a ratio of the total number of rows (e.g. nrows / 10)
• When the data is very big, limit it to a certain maximum size (e.g. whether data is 20GB or 300GB, pick 10_000_000 rows)
• If the same analysis will be rerun many times, benchmark different chunksize choices and pick the one that is fastest but also doesn't cause OOM errors
• etc.

Showing an example of how to do that benchmarking would be really useful to users who are lost on what chunksize to pick.