add CC license

Author: davidjenni

README.md

@@ -73,3 +73,5 @@ HJKL as cursor keys are more ergonomical to reach by moving the FN to the left C
 The how-to for these mappings is from 2 reddit threads:
 * [r/mk: HowTo program pok3r](http://www.reddit.com/r/MechanicalKeyboards/comments/35uy60/guide_howto_program_your_pok3r_programming_layers/)
 * [r/mk: HowTo media controls pok3r](http://www.reddit.com/r/MechanicalKeyboards/comments/37j3sx/guide_modification_pok3r_media_volume_controls_hw/)
+ 
+<a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-sa/4.0/88x31.png" /></a><br />This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>.