adding some links to readmine for better discoverability of content/contact...

adding some links to readmine for better discoverability of content/contact methods that help people to migrate. 
related issue is: tails/tails#17722

README

-doc/README
\ No newline at end of file
+Tails is a portable operating system that protects your privacy
+and helps you avoid censorship.
+https://tails.boum.org/
+
+How to contribute to Tails: 
+https://tails.boum.org/contribute/index.en.html
+
+How to get started with Gitlab: 
+https://tails.boum.org/contribute/working_together/GitLab/
+
+How to transition to GitLab: 
+https://tails.boum.org/contribute/working_together/GitLab/transition/
+
+Contact:
+email: https://tails.boum.org/about/contact/index.en.html
+xmpp: tails@conference.riseup.net and tails-dev@conference.riseup.net
+fediverse: https://fosstodon.org/@tails