Update join.html
Update join.html

Adding more links, e.g. Facebook
gvwilson/website,rgaiacs/swc-website,rgaiacs/swc-website,ErinBecker/website,k8hertweck/website,rgaiacs/swc-website,gvwilson/website,swcarpentry/website,ErinBecker/website,k8hertweck/website,swcarpentry/website,swcarpentry/website,k8hertweck/website,gvwilson/website,gvwilson/website,gvwilson/website,k8hertweck/website,rgaiacs/swc-website,ErinBecker/website,swcarpentry/website,swcarpentry/website,ErinBecker/website,k8hertweck/website,ErinBecker/website,rgaiacs/swc-website