Merge pull request #13 from learning-process/cc-lic

Add CC license for content

Author: allnes

README.md

@@ -1,3 +1,5 @@
 [![Build](https://github.com/learning-process/parallel_programming_slides/actions/workflows/build.yml/badge.svg)](https://github.com/learning-process/parallel_programming_slides/actions/workflows/build.yml)
 
 # Slides for parallel programming course
+
+[![License: CC BY 4.0](https://img.shields.io/badge/License-CC%20BY%204.0-lightgrey.svg)](https://creativecommons.org/licenses/by/4.0/)