Add CODEOWNERS file

The CODEOWNERS file can be parsed by GitHub to suggest reviewers for
PRs. The actual permsissions are defined in the GitHub configuration.

More details about maintainers and emeritus are tracked as comment.

Signed-off-by: Andrea Frittoli <[email protected]>

Author: afrittoli

CODEOWNERS

@@ -0,0 +1,11 @@
+# Maintainers table
+# | Full Name         | Company    | GitHub                                                         |
+# |-------------------|:----------:|----------------------------------------------------------------|
+# | Emil Bäckmark     | Ericsson   | [@e-backmark-ericsson](https://github.com/e-backmark-ericsson) |
+# | Andrea Frittoli   | IBM        | [@afrittoli](https://github.com/afrittoli)                     |
+
+# Emeritus maintainers (must be in a comment)
+# Note yet
+
+# Repo maintainers
+* @cdevents/spec-maintainers