fix(devops): Correct precedence in CODEOWNERS file (#40)

# Motivation
In GitHub codeowners files, the last matching entry, not the first,
takes precedence. This is mentioned in [the CODEOWNERS
example](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners#example-of-a-codeowners-file).
The CODEOWNERS file was written assuming that the first match takes
precendence.

# Changes
- Reverse the entries in the codeowners file and add a comment
explaining the order.

# Tests
<!-- Please provide any information or screenshots about the tests that
have been done -->

.github/CODEOWNERS

@@ -1,5 +1,8 @@
+# IMPORTANT: The last matching entry has the highest precedence.
+
+# The GIX team members who maintain this repo:
+* @bitdivine
+
 # The codebase is owned by the Governance & Identity Experience team at DFINITY
 # For questions, reach out to: <gix@dfinity.org>
 .github/CODEOWNERS @dfinity/gix
-# The GIX team members who maintain this repo:
-* @bitdivine