Set Zenodo badge and link

Author: jl-wynen

docs/about/index.md

@@ -12,7 +12,7 @@ ESSreflectometry is available as open source under the [BSD-3 license](https://o
 
 Please cite the following:
 
-[![DOI](https://zenodo.org/badge/FIXME.svg)](https://zenodo.org/doi/10.5281/zenodo.FIXME)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.10117675.svg)](https://zenodo.org/doi/10.5281/zenodo.10117675)
 
 To cite a specific version of ESSreflectometry, select the desired version on Zenodo to get the corresponding DOI.