Fonts lack latin-ext support

[bartekpl]

Hi, just wanted you to know that font files do not contain some diacritical characters required in languages such as Polish (several examples: ń ź Ę Ź Ż Ć). I understand that not every site needs this additional character set so it may be a good idea to add an option in _config.yml which would make it available if needed. I'd add it myself but honestly I don't know how to get these files as you have them - any tips are welcome, I can do it then :).

PS. Is there any particular reason that fonts are actually in local files? Why not as references to Google Fonts?