support less vars for tabs title font size

components/style/themes/default.less

@@ -387,6 +387,8 @@
 @tabs-card-height: 40px;
 @tabs-card-active-color: @primary-color;
 @tabs-title-font-size: @font-size-base;
+@tabs-title-font-size-lg: @font-size-sm;
+@tabs-title-font-size-sm: @font-size-base;
 @tabs-ink-bar-bg-color: @primary-color;
 @tab-bar-margin: 0 0 16px 0;
 @tab-horizontal-margin: 0 32px 0 0;

components/tabs/style/index.less

@@ -207,7 +207,7 @@
   }
 
   &-large &-nav-container {
-    font-size: @font-size-lg;
+    font-size: @tabs-title-font-size-lg;
   }
 
   &-large &-tab {
@@ -215,7 +215,7 @@
   }
 
   &-small &-nav-container {
-    font-size: @font-size-base;
+    font-size: @tabs-title-font-size-sm;
   }
 
   &-small &-tab {