Keep ia0 as owner of rust Changelogs (#1168)

The `*.md` rule for documentation is a bit strong. The intent was only to capture READMEs under
rust, so this PR explicitly excludes the CHANGELOGs from that rule. This makes it possible to do
pure code changes to the Rust CLI and library without double approvals.

Author: ia0

.github/CODEOWNERS

@@ -9,6 +9,9 @@
 *.md @reyammer
 /tests_data/ @reyammer
 
+# Julien still owns the Rust changelogs
+/rust/**/CHANGELOG.md @ia0
+
 # Luca owns the JS code, docs, and website
 /js/ @invernizzi
 /docs/js.md @invernizzi