Validated input text fields to enter only blank spaces

Author: RonakParmar

app/code/Magento/CatalogSearch/view/frontend/templates/advanced/form.phtml

@@ -126,7 +126,8 @@
                        value="<?= $block->escapeHtml($block->getAttributeValue($_attribute)) ?>"
                        title="<?= $block->escapeHtml($block->getAttributeLabel($_attribute)) ?>"
                        class="input-text <?= $block->escapeHtmlAttr($block->getAttributeValidationClass($_attribute)) ?>"
-                       maxlength="<?= $block->escapeHtmlAttr($maxQueryLength) ?>" />
+                       maxlength="<?= $block->escapeHtmlAttr($maxQueryLength) ?>"
+                       data-validate="{'validate-alphanum':true}"/>
             <?php endswitch; ?>
             </div>
         </div>