style: modify toolbar style.

Author: jaywcjlove

core/src/components/Toolbar/index.less

@@ -4,7 +4,7 @@
   &-toolbar {
     border-bottom: 1px solid var(--md-editor-box-shadow-color);
     background-color: var(--md-editor-background-color);
-    padding: 5px 5px;
+    padding: 3px;
     display: flex;
     justify-content: space-between;
     align-items: center;