enhance(ui): hide code lang flag when narrow screen size

src/main/frontend/extensions/code.css

@@ -14,11 +14,11 @@
     width: fit-content;
     /* height:2rem; */
     order: 3;
-    display: flex;
     left: auto;
     right: 0;
     /* margin-top: 4px; */
     z-index: 9999;
+    display: none;
   }
 
   &-calc {
@@ -33,6 +33,12 @@
       font-family: Fira Code, Monaco, Menlo, Consolas, 'COURIER NEW', monospace;
     }
   }
+
+  @screen md {
+    &-lang {
+      display: flex;
+    }
+  }
 }
 
 .CodeMirror {