rn-49: add radicle tool news

Author: chriscool

rev_news/drafts/edition-49.md

@@ -52,6 +52,9 @@ __Git tools and sites__
  an improved sequence editor for Git interactive rebase by
 [MitMaro](https://github.com/MitMaro).
 
+*[radicle](http://radicle.xyz/) is a peer-to-peer stack for code
+ collaboration based on Git and [IPFS](https://ipfs.io/).
+
 ## Credits
 
 This edition of Git Rev News was curated by