Update README.md

Author: flavio20002

README.md

@@ -10,4 +10,15 @@ This template was realized with the help of:
 
 https://github.com/sahasatvik/typst-theorems
 
-https://github.com/RolfBremer/in-dexter
+https://github.com/RolfBremer/in-dexter
+
+Shield: [![CC BY-NC-SA 4.0][cc-by-nc-sa-shield]][cc-by-nc-sa]
+
+This work is licensed under a
+[Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License][cc-by-nc-sa].
+
+[![CC BY-NC-SA 4.0][cc-by-nc-sa-image]][cc-by-nc-sa]
+
+[cc-by-nc-sa]: http://creativecommons.org/licenses/by-nc-sa/4.0/
+[cc-by-nc-sa-image]: https://licensebuttons.net/l/by-nc-sa/4.0/88x31.png
+[cc-by-nc-sa-shield]: https://img.shields.io/badge/License-CC%20BY--NC--SA%204.0-lightgrey.svg