DEV: Rename search -> welcome banner (#144)

Horizon is targeting the welcome banner not the search component
anymore, update CSS class names and rename the file to make this clearer

common/common.scss

@@ -11,7 +11,7 @@
 @import "misc";
 @import "mobile-stuff";
 @import "nav-pills";
-@import "search-banner";
+@import "welcome-banner";
 @import "sidebar";
 @import "sidebar-new-topic-button";
 @import "topic";

scss/welcome-banner.scss

@@ -2,7 +2,7 @@
   z-index: calc(z("base") + 1);
 }
 
-.custom-search-banner-wrap {
+.welcome-banner__wrap {
   display: grid;
   grid-template-rows: 0.33fr 0.33fr 0.33fr;
   grid-template-columns: 1fr 1fr;
@@ -11,9 +11,17 @@
   border-bottom: 1px solid var(--primary-300);
   padding: 1.5em 0 2.5em;
   margin-bottom: 0;
+
   @media screen and (max-width: 768px) {
     padding: 1em;
   }
+
+  @include breakpoint("mobile-extra-large") {
+    display: block;
+    padding: 0.5em;
+    margin-top: 0;
+  }
+
   h1 {
     grid-column: 1/2;
     grid-row: 1/-1;
@@ -41,7 +49,11 @@
       text-align: center;
       margin-bottom: 0.5em;
     }
+    @include breakpoint("mobile-extra-large") {
+      font-size: var(--font-up-2);
+    }
   }
+
   .search-menu {
     grid-column: 2/3;
     grid-row: 1/-1;
@@ -59,6 +71,9 @@
       grid-row: 2/-1;
       grid-column: 1/-1;
     }
+    @include breakpoint("mobile-extra-large") {
+      display: none;
+    }
   }
   p {
     display: none;