Add Zenodo badge

Author: anitagraser

README.md

@@ -4,6 +4,7 @@
 [![Docker Status](https://img.shields.io/docker/automated/qgis/qgis.svg)](https://hub.docker.com/r/qgis/qgis/tags)
 [![Build Status](https://dev.azure.com/qgis/QGIS/_apis/build/status/qgis.QGIS?branchName=master)](https://dev.azure.com/qgis/QGIS/_build/latest?definitionId=1&branchName=master)
 [![Windows cross build](https://github.com/qgis/QGIS/workflows/MingW64%20Windows%2064bit%20Build/badge.svg)](https://github.com/qgis/QGIS/actions/workflows/mingw64.yml?query=branch%3Amaster+event%3Apush)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.5869837.svg)](https://doi.org/10.5281/zenodo.5869837)
 
 QGIS is a full-featured, user-friendly, free-and-open-source (FOSS) geographical information system (GIS) that runs on Unix platforms, Windows, and MacOS.