Added quotation marks to metadata

README.md

@@ -2,9 +2,9 @@
 language:
 - {en}
 
-license: {cc-by-nc-sa-4.0}
-license_name: {Creative Commons Attribution Non Commercial Share Alike 4.0}
-license_link: {https://creativecommons.org/licenses/by-nc-sa/4.0/}
+license: {"cc-by-nc-sa-4.0"}
+license_name: {"Creative Commons Attribution Non Commercial Share Alike 4.0"}
+license_link: {"https://creativecommons.org/licenses/by-nc-sa/4.0/"}
 
 tags:
 - {motivation}