adding doi

Signed-off-by: Vanessa Sochat <[email protected]>

Author: vsoch

README.md

@@ -1,5 +1,7 @@
 # Singularity Compose
 
+[![DOI](https://zenodo.org/badge/188852712.svg)](https://zenodo.org/badge/latestdoi/188852712)
+
 This is a simple orchestration library for Singularity containers, akin to
 Docker Compose. See the [specification](https://singularityhub.github.io/singularity-compose/#/spec/spec-1.0) 
 and the [documentation](https://singularityhub.github.io/singularity-compose) for