Fix CodeEditor scroll bug

Author: velopert

velog-frontend/src/components/write/CodeEditor/CodeEditor.scss

@@ -22,8 +22,9 @@
     min-width: 0;
     flex: 1;
     display: flex;
+    flex-direction: column;
     .CodeMirror {
-      height: 100%;
+      flex: 1;
       padding-top: 1rem;
       padding-bottom: 1rem;
       @include media('<large') {