Upgrade Font Awesome 5.0 icons

[joewheaton]

@MattReimer what are the implications of moving from the Font Awesome 4.x to 5 or 6.x? Would it break all our current references to it, or still work? As we enter a phase of upping our game on marketing, documentation, etc. it might be nice to have that richer range of icons for authors of content to use?

Obviously a low priority, but thought I'd ask.

[MattReimer]

Should be fine I think. We'll need to keep track of everywhere icons are used but most should have backwards compatibility

[joewheaton]

As far as I am aware, it is in virtually all sites using the template...

[MattReimer]

Did a quick test and it seems like the major version upgrade isn't compatible with what we're doing. This is a bigger effort so let's push it to do at the same time as the Jekyll 4.0 upgrade #13