fixup! README.md: Add a Windows-specific preamble

Add the Contributor Covenant badge to the `README.md`.

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

README.md

@@ -1,6 +1,7 @@
 Git for Windows
 ===============
 
+[![Contributor Covenant](https://img.shields.io/badge/Contributor%20Covenant-2.1-4baaaa.svg)](CODE_OF_CONDUCT.md)
 [![Open in Visual Studio Code](https://img.shields.io/static/v1?logo=visualstudiocode&label=&message=Open%20in%20Visual%20Studio%20Code&labelColor=2c2c32&color=007acc&logoColor=007acc)](https://open.vscode.dev/git-for-windows/git)
 [![Build status](https://github.com/git-for-windows/git/workflows/CI/badge.svg)](https://github.com/git-for-windows/git/actions?query=branch%3Amain+event%3Apush)
 [![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)