You're right, the default page size (A5) and font size are things that need to be easily customizable. I resisted adding many options to the CLI, but I think this is a good way to solve it? https://github.com/danburzo/percollate/issues/27
It's probably a good idea to not introduce flags like `--font-size 12p` or `--page A4` since it leads down a rabbit hole. (Where do you stop?). Directly passing down CSS seems appropriate here.
