config: add trailingSlash: true for better SEO

- https://stackoverflow.com/questions/57347590/remove-trailing-slash-on-github-page-hosted-website
- https://stackoverflow.com/questions/77693243/using-cloudflare-to-add-trailing-slash-to-url
- https://stackoverflow.com/questions/54727643/trailing-slashes-in-jekyll-github-pages-site-cause-404

docusaurus.config.ts

@@ -16,6 +16,7 @@ const config: Config = {
   baseUrl: "/",
 
   deploymentBranch: "gh-pages",
+  trailingSlash: true,
 
   // GitHub pages deployment config.
   // If you aren't using GitHub pages, you don't need these.