feat(css): set breakpoints the de facto value

768px has been much more common for many years (since 2010), and
other major CSS frameworks have used 768px as the breakpoint for
years.

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Author: tnir

packages/docsearch-css/src/button.css

@@ -63,7 +63,7 @@
   width: 20px;
 }
 
-@media (max-width: 750px) {
+@media (max-width: 768px) {
   .DocSearch-Button-Keys,
   .DocSearch-Button-Placeholder {
     display: none;

packages/docsearch-css/src/modal.css

@@ -556,7 +556,7 @@ svg.DocSearch-Hit-Select-Icon {
 }
 
 /* Responsive */
-@media (max-width: 750px) {
+@media (max-width: 768px) {
   :root {
     --docsearch-spacing: 10px;
     --docsearch-footer-height: 40px;

packages/docsearch-react/src/DocSearchModal.tsx

@@ -332,7 +332,7 @@ export function DocSearchModal({
   }, []);
 
   React.useEffect(() => {
-    const isMobileMediaQuery = window.matchMedia('(max-width: 750px)');
+    const isMobileMediaQuery = window.matchMedia('(max-width: 768px)');
 
     if (isMobileMediaQuery.matches) {
       snippetLength.current = 5;