docs: fix position of search modal to avoid interface blocking at small breakpoints

Author: mrholek

docs/assets/scss/_search.scss

@@ -29,6 +29,7 @@
   --docsearch-muted-color: var(--cui-secondary-color);
   --docsearch-hit-shadow: none;
 
+  position: fixed;
   z-index: 2000; // Make sure to be over all components showcased in the documentation
   cursor: auto; // Needed because of [role="button"] in Algolia search modal. Remove once https://github.com/algolia/docsearch/issues/1370 is tackled.