Create CODEOWNERS

See: https://github.com/blog/2392-introducing-code-owners

Author: Kristján Oddsson

.github/CODEOWNERS

@@ -0,0 +1,5 @@
+# Lines starting with '#' are comments.
+# Each line is a file pattern followed by one or more owners.
+
+# These owners will be the default owners for everything in the repo.
+*       @koddsson @kristjanmik @benediktvaldez @MiniGod