fix(core): feedback from @ccoVeille

Co-authored-by: ccoVeille <ccoVeille@users.noreply.github.com>

harper-core/src/linting/oxford_comma.rs

@@ -81,7 +81,7 @@ impl Linter for OxfordComma {
     }
 
     fn description(&self) -> &str {
-        "The Oxford comma is one of the more controversial rules in common use today. Enabling this lint checks that there is a comma before `and` or `or` when listing out more than two ideas."
+        "The Oxford comma is one of the more controversial rules in common use today. Enabling this lint checks that there is a comma before `and`, `or`, or `nor` when listing out more than two ideas."
     }
 }