README.md: Add a Windows-specific preamble

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

README.md

@@ -1,3 +1,19 @@
+Git for Windows
+===============
+
+[![Join the chat at https://gitter.im/git-for-windows/git](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/git-for-windows/git?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
+This is [Git for Windows](http://git-for-windows.github.io/), the Windows port
+of [Git](http://git-scm.com/).
+
+The Git for Windows project is run using a [governance
+model](http://git-for-windows.github.io/governance-model.html). If you
+encounter problems, you can report them as [GitHub
+issues](https://github.com/git-for-windows/git/issues), discuss them on Git
+for Windows' [Google Group](http://groups.google.com/group/git-for-windows),
+and [contribute bug
+fixes](https://github.com/git-for-windows/git/wiki/How-to-participate).
+
 Git - fast, scalable, distributed revision control system
 =========================================================