Fix case-sensitive search term in example. (#4024)

* Fix case-sensitive search term in example.

Converting both the name and search value to lowercase solves case sensitive searching.

* Update thinking-in-react.md

* Update thinking-in-react.md

* Update thinking-in-react.md

Co-authored-by: Dan Abramov <dan.abramov@gmail.com>

beta/src/pages/learn/thinking-in-react.md

@@ -346,7 +346,11 @@ function ProductTable({ products, filterText, inStockOnly }) {
   let lastCategory = null;
 
   products.forEach((product) => {
-    if (product.name.indexOf(filterText) === -1) {
+    if (
+      product.name.toLowerCase().indexOf(
+        filterText.toLowerCase()
+      ) === -1
+    ) {
       return;
     }
     if (inStockOnly && !product.stocked) {
@@ -533,7 +537,11 @@ function ProductTable({ products, filterText, inStockOnly }) {
   let lastCategory = null;
 
   products.forEach((product) => {
-    if (product.name.indexOf(filterText) === -1) {
+    if (
+      product.name.toLowerCase().indexOf(
+        filterText.toLowerCase()
+      ) === -1
+    ) {
       return;
     }
     if (inStockOnly && !product.stocked) {