feature add top horizontal scroll bar done VERSION v1.0 release

Asset/css/shrink-vertically.css

@@ -32,3 +32,19 @@
     max-height: calc(100vh - var(--sv-shrink-offset, 240px)) !important;
     min-height: 0 !important;
 }
+
+/*
+ * Optional top horizontal scrollbar (added by Asset/js/top-scrollbar.js when the
+ * "Add a top horizontal scrollbar" setting is enabled). The inner element is given a
+ * width equal to the board's scrollable width by the script; overflow-x: auto then
+ * produces a scrollbar whose range mirrors the board's own bottom scrollbar. The 1px
+ * inner height keeps the bar to just the scrollbar itself.
+ */
+.sv-top-scroll {
+    overflow-x: auto;
+    overflow-y: hidden;
+}
+
+.sv-top-scroll-inner {
+    height: 1px;
+}