IBX-11374: Fixed dropdown menu

Author: OstafinL

src/bundle/Resources/public/scss/_dropdown-popover.scss

@@ -16,3 +16,9 @@
         color: initial;
     }
 }
+
+.ibexa-search-view {
+    .ibexa-dropdown-popover {
+        z-index: 1060;
+    }
+}

src/bundle/Resources/public/scss/_main-header.scss

@@ -1,4 +1,6 @@
 .ibexa-main-header {
+    position: relative;
+    z-index: 1080;
     width: 100%;
     display: flex;
     justify-content: space-between;