FEAT: Add .sort_keys()

src/lib.rs

@@ -1110,6 +1110,16 @@ impl<K, V, S> OrderMap<K, V, S>
         });
     }
 
+    /// Sort the map’s key-value pairs by the default ordering of the keys
+    pub fn sort_keys(&mut self)
+        where K: Ord,
+    {
+        self.sort_by(|k1, _, k2, _| Ord::cmp(k1, k2))
+    }
+
+    /// Sort the map’s key-value pairs in place using the comparison
+    /// function `compare`; the comparison function receives two key and
+    /// value pairs to compare (so you can sort by keys or values).
     pub fn sort_by<F>(&mut self, mut compare: F)
         where F: FnMut(&K, &V, &K, &V) -> Ordering,
     {