Support showing Discord profile on about page

[dtch1997]

Is your feature request related to a problem? Please describe.
I use Discord a lot for loose professional mingling. It would be ideal for me to link my Discord profile on my 'about' page, similar to how many other social media links are already integrated.

Describe the solution you'd like
I would like some quick pointers on how I can set up my about page to show my Discord link, preferably with the Discord icon.

[dtch1997]

I figured out how to do this by reading the conversation here: #313

We just need to add a flag in _config.yaml and add a corresponding line in _includes/social.html.