Add PISA 2022 data

[jzuccollo]

Hi, are you planning to add the 2022 dataset to this package at some point? I notice there haven't been any updates for a while, though, so apologies if this isn't the currently maintained repo for this package.

[dicook]

Hi @jzuccollo Ideally we will add this data soon.

[kevinwang09]

Added in the GitHub version now: student_full_data/student_2022.rds

We are preparing a submission to CRAN soon.