try to prevent getting garbled icon font icons
try to prevent getting garbled icon font icons

Every once in a while I’ll load a page and I’ll get icons that look
Like this: https://cl.ly/a24f9fdf8825

This is an attempt to maybe fix that.

According to: https://font-display.glitch.me/
“If you're using a web font for icons, there is no acceptable fallback 
font you can render these icons in (unless you're using emoji or 
something), so your only option is to completely block until the font 
is ready, with font-display:block.”

Test plan:
* I don’t know how to reliably reproduce getting the weird icons but
  This commit shouldn’t hurt. 
* once this is in prod, it should happen less

Change-Id: Ic922cb6378d7d73782c05ec2ba5823da38a9edb7
Reviewed-on: https://gerrit.instructure.com/195929
Tested-by: Jenkins
Reviewed-by: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
QA-Review: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms