Add license

README.md

@@ -195,3 +195,9 @@
 * [**Rust**: *Building a DNS server in Rust*](https://github.com/EmilHernvall/dnsguide/blob/master/README.md)
 
 **[[Submit tutorial](https://github.com/danistefanovic/build-your-own-x/issues/new)]**
+
+## License
+
+[![CC0](http://mirrors.creativecommons.org/presskit/buttons/88x31/svg/cc-zero.svg)](https://creativecommons.org/publicdomain/zero/1.0/)
+
+To the extent possible under law, [Daniel Stefanovic](http://twitter.com/danistefanovic) has waived all copyright and related or neighboring rights to this work.