Add youtube and discord links as logos, c.f. the github and twitter links

[spencerahill]

Write now the youtube link is in text...this would make it pop out more.

And link to discord server does not yet exist

[spencerahill]

And keep the youtube link as text but rename it "videos"

[NorrisKhoo]

I added an icon for the YouTube channel and renamed its link to "videos"