fix(abc:st): fix click trigger on blank area of sub-menus (#1534)

Author: cipchk

packages/abc/st/style/index.less

@@ -23,6 +23,7 @@
   &__btn {
     &-sub {
       @{st-prefix}__btn-text {
+        width: 100%;
         color: inherit;
       }
     }