Create CODEOWNERS for Ruby maintainers

Add CODEOWNERS file to define default reviewers.

Signed-off-by: Jan Kowalleck <[email protected]>

Author: jkowalleck

.github/CODEOWNERS

@@ -0,0 +1,6 @@
+# see https://docs.github.com/en/github/creating-cloning-and-archiving-repositories/about-code-owners
+
+
+# all maintainers are default-reviewers of new pull requests.
+# see https://github.com/orgs/CycloneDX/teams/ruby-maintainers
+*  @CycloneDX/ruby-maintainers