Add the possibility to use font Aptos in PowerBI theme

[NiekR]

We would like to use font Aptos in PowerBI. This is the new default font in Office 365, but it is not selectable in the PowerBI UI and it is also not possible to put it in a theme json file.

The reason is that the Aptos font is not located in "C:\Windows\Fonts" but in "C:\Users\YOUR_USERNAME\AppData\Local\Microsoft\FontCache\4\CloudFonts". It seems the theme json only supports fonts located in "C:\Windows\Fonts".