Add DOI to README file

README.md

@@ -6,7 +6,7 @@ Caltech DIBS ("_**Di**gital **B**orrowing **S**ystem_") is the Caltech Library's
 [![License](https://img.shields.io/badge/License-BSD%203--Clause-blue.svg?style=flat-square)](https://choosealicense.com/licenses/bsd-3-clause)
 [![Python](https://img.shields.io/badge/Python-3.8+-brightgreen.svg?style=flat-square)](https://www.python.org/downloads/release/python-380/)
 [![Latest release](https://img.shields.io/github/v/release/caltechlibrary/dibs.svg?style=flat-square&color=b44e88)](https://github.com/caltechlibrary/dibs/releases)
-
+[![DOI](https://img.shields.io/badge/dynamic/json.svg?label=DOI&style=flat-square&color=lightgray&query=$.metadata.doi&uri=https://data.caltech.edu/api/record/1959)](https://data.caltech.edu/records/1959)
 
 Table of contents
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