Add push_extra method to Context

src/context.rs

@@ -37,6 +37,10 @@ impl Context {
         &mut self.extra
     }
 
+    pub fn push_extra(&mut self, detail: Detail) {
+        self.extra.push(detail);
+    }
+
     pub fn pop_extra(&mut self) -> Option<Detail> {
         self.extra.pop()
     }