Add DOI badge

Author: mr-c

README.md

@@ -1,6 +1,8 @@
+[![DOI](https://zenodo.org/badge/89621457.svg)](https://zenodo.org/badge/latestdoi/89621457)
 
-WIP re-structuring and expansion of the CWL v1.0 user guide
+User guide for CWL v1.0.1
 
+Original source:
 http://www.commonwl.org/v1.0/UserGuide.html
 which is built from
 https://github.com/common-workflow-language/common-workflow-language/blob/master/v1.0/UserGuide.yml