Varying font size

## Expected Behavior

I'm expecting to be able to alter the styling of the text inside the table, specifically the font size.

## Current Behavior

I've tried working with the example in code sandbox:

https://codesandbox.io/embed/0ylq1lqwp0

and adding a line like:

fontSize: "2pt"

In various places including underneath `overrides->MUIDataTable->root` and a number places under `overrides->MUIDataTableBodyCell` (based on a variety of sources) including `root`, `typography`, `tablecell`, `data`.

Looking at the Chrome debugger, it looks like the styles for `MuiTableCell-body`, and `MUIDataTableBodyCell-root` are being overwritten by `MUIDataTableBodyCell-responsiveStacked`, but I can't figure out how to target that style :(

## Steps to Reproduce (for bugs)

You can reproduce just by using this example:

https://codesandbox.io/embed/0ylq1lqwp0

I'm hoping an expert can just show me exactly where I need to specify my font size and it might be a useful example for the documentation in general.

I'd actually also like to specify the padding on the table cells, but I'm hoping if I know where to specify font size that should also be easier :)

## Your Environment

Using whatever is being used in codesandbox.io by default.