Create CODEOWNERS (#661)

A codeowners file makes it so people are automatically suggested as reviewers for pull requests
based on path to the code in the PR.

More information can be found here: 
https://docs.github.com/en/free-pro-team@latest/github/creating-cloning-and-archiving-repositories/about-code-owners

Co-authored-by: Luke Hinds <7058938+lukehinds@users.noreply.github.com>

.github/CODEOWNERS

@@ -0,0 +1 @@
+*       @ericwb @lukehinds @ghugo @sigmavirus24