people: Consider additional links

[effigies]

What other profiles do people have that they might want to add to their links?

We currently have website, ORCID and GitHub. Anything else? Or is this dense enough?

https://github.com/poldracklab/poldracklab.github.io/blob/main/people.yml

[ricardjocelyn]

Could add twitter? and a section for rotation students and undergraduates/volunteers?

[effigies]

Broke out the latter idea into its own issue. I'm a little worried about adding non-academic social media, as there are lots of those. Can people thumbs up/down comments with icons they would (not) like to see added?