fix(mobile nav): Better? fix for mobile nav pos using has()

This targets the mobile nav and adds spacing to account for the banner, jsut like the previous css does, without changing the fixed position of the mobile nav menu to absolute.

static/css/s2.css

@@ -616,6 +616,12 @@ input.noselect {
   z-index: 1000;
   overflow-y: scroll;
 }
+div:has(#bannerMessage) + .readerApp.singlePanel .mobileNavMenu {
+  position: fixed; /*This takes the 60px of the header plus 120px of the banner into account */
+  height: calc(100vh - 180px);
+  top: 180px;
+}
+
 .mobileNavMenu.closed {
   display: none;
 }