Update socials on all websites

[rempsyc]

We should probably update our socials if pkgdown supports that

[strengejacke]

@IndrajeetPatil ?

[IndrajeetPatil]

TBH, I am no longer an active consumer of social media, so I don't feel too strongly either way.

If you wish to proceed with this, pkgdown allows adding multiple social media accounts via metadata:

https://pkgdown.r-lib.org/articles/metadata.html