add link to git slides

week02-feb25/README.md

-# Week 2: An introduction to *git*, *GitHub* and *GitLab*
+# Week 2: A practical introduction to *git*/*GitLab*
 
-> More info forthcoming!
+I'm giving you all edit access to [this document](https://docs.google.com/presentation/d/1Kg54GCAIRxQYe0mzz72e-rRlhCpZipLNi7MuYU4TKZE/edit?usp=sharing), so only honour stops you from destroying it.