Add Emoji support

[jhogervorst]

I'm opening this issue since I am using dompdf in a project, and currently it doesn't support showing emoji characters (even when loading a compatible font, like Noto Emoji). There's already an issue requesting emoji support in the dompdf repo (https://github.com/dompdf/dompdf/issues/1698), but according to the replies there, emojis should first be supported in php-font-lib.

[AndyGaskell]

This seems an ok short term workaround... https://www.beaubus.com/blog/add_emoji_support_to_dompdf.html