adding zenodo DOI

Signed-off-by: vsoch <[email protected]>

Author: vsoch

README.md

@@ -1,6 +1,7 @@
 # Singularity Registry HPC (shpc)
 
 [![GitHub actions status](https://github.com/singularityhub/singularity-hpc/workflows/singularity-hpc/badge.svg?branch=main)](https://github.com/singularityhub/singularity-hpc/actions?query=branch%3Amain+workflow%3Asingularity-hpc)
+[![DOI](https://zenodo.org/badge/354130612.svg)](https://zenodo.org/badge/latestdoi/354130612)
 
 ![https://raw.githubusercontent.com/singularityhub/singularity-hpc/main/docs/assets/img/shpc.png](https://raw.githubusercontent.com/singularityhub/singularity-hpc/main/docs/assets/img/shpc.png)