How do I add font sizes to the HTML field?

Hi Team,

Hoping a simple one for you all today.  I would like to add a number of 'font sizes' to the HTML field dropdown - I can add new fonts by updating a property, but haven't found where I can the sizes?

OOTB the sizes seem random - as you can see if you create a question, or reply, it he community itself, the sizes go from 18pt to 24 pt, I'd like to add the 20 and 22pt fonts to this list.

Any help is appreciated.

Cheers

Carl.