Fonts aren't applied when the network speed is low

[Crocmagnon]

Describe the bug

When displaying the site on a device with a low network speed, the custom fonts are loaded afterwards and aren't applied.

Steps to reproduce (if necessary)

Use the dev tools of your browser to throttle the connection quality to 3G-like.

See this screencast.

Expected behavior

Either fonts should be applied after being downloaded or they should not be downloaded at all. Right now it's just a waste of resource.

Application configuration

• Single mode or Multi-user mode? Single
• Database? [mysql/sqlite] sqlite
• Open registration? [yes/no] no
• Federation enabled? [yes/no] no

Version or last commit: 037fc40