If you are using a long URL, such as example.com/files/folder/sitemap.html, you can change it to "example.com/sitemap" using htaccess.
To do that, you only need to modify the line below according to your needs, and then add this code to your htaccess file.
RewriteEngine on
RewriteRule ^sitemap/$ /files/folder/sitemap.html [L]
