- YahooGroups: added readme file

git-svn-id: http://svn.miranda-ng.org/main/trunk@4356 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c
git-svn-id: http://svn.miranda-ng.org/main/trunk@4357 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c