Add functionality to turn off / disable afcharts

[alice-hannah]

It's currently difficult to revert defaults set using use_afcharts. The workaround is to use afcharts functions on each chart individually, but it might be useful for some to be able to 'stop using afcharts'. Not sure yet how difficult this would be to do and whether it's worth it.

Possible solutions:

• theme_xaringan_restore_defaults: https://github.com/gadenbuie/xaringanthemer/blob/HEAD/R/ggplot2.R
• @Olivia-Box-Power mentioned devtools function to switch modes (?)

[Olivia-Box-Power]

This may be easier in the next version of ggplot2

rest aesthetics