ci(CODEOWNERS): add content team for npm dependencies (#480)

Author: caugner

.github/CODEOWNERS

@@ -10,5 +10,5 @@
 /.github/workflows/ @mdn/engineering
 /.github/CODEOWNERS @mdn/engineering
 /SECURITY.md        @mdn/engineering
-/package.json       @mdn/engineering @mdn-bot
-/package-lock.json  @mdn/engineering @mdn-bot
+/package.json       @mdn/content-team @mdn-bot
+/package-lock.json  @mdn/content-team @mdn-bot