docs(trailing-slash): add Trailing Slash Middleware (honojs#284)

.vitepress/config.ts

@@ -118,11 +118,12 @@ const sidebars = (): DefaultTheme.SidebarItem[] => [
       { text: 'ETag', link: '/middleware/builtin/etag' },
       { text: 'JSX Renderer', link: '/middleware/builtin/jsx-renderer' },
       { text: 'JWT', link: '/middleware/builtin/jwt' },
-      { text: 'Timing', link: '/middleware/builtin/timing' },
       { text: 'Logger', link: '/middleware/builtin/logger' },
       { text: 'Method Override', link: '/middleware/builtin/method-override' },
       { text: 'Pretty JSON', link: '/middleware/builtin/pretty-json' },
       { text: 'Secure Headers', link: '/middleware/builtin/secure-headers' },
+      { text: 'Timing', link: '/middleware/builtin/timing' },
+      { text: 'Trailing Slash', link: '/middleware/builtin/trailing-slash' },
       { text: '3rd-party Middleware', link: '/middleware/third-party' },
     ],
   },

middleware/builtin/trailing-slash.md

@@ -0,0 +1,51 @@
+# Tailing Slash Middleware
+
+This middleware resolves the handling of Trailing Slashes in GET requests.
+
+`appendTrailingSlash` redirects to the URL to which it added the Tailing Slash if the content was not found. Also, `trimTrailingSlash` will remove the Tailing Slash.
+
+## Import
+
+::: code-group
+
+```ts [npm]
+import { Hono } from 'hono'
+import { appendTrailingSlash, trimTrailingSlash } from 'hono/trailing-slash'
+```
+
+```ts [Deno]
+import { Hono } from 'https://deno.land/x/hono/mod.ts'
+import { appendTrailingSlash, trimTrailingSlash } from 'https://deno.land/x/hono/middleware.ts'
+```
+
+:::
+
+## Usage
+
+Example of redirecting a GET request to `/about/me` to `/about/me/`.
+
+```ts
+import { Hono } from 'hono'
+import { appendTrailingSlash } from 'hono/trailing-slash'
+
+const app = new Hono({ strict: true })
+
+app.use(appendTrailingSlash())
+app.get('/about/me/', (c) => c.text('With Trailing Slash'))
+```
+
+Example of redirecting a GET request to `/about/me/` to `/about/me`.
+
+```ts
+import { Hono } from 'hono'
+import { trimTrailingSlash } from 'hono/trailing-slash'
+
+const app = new Hono({ strict: true })
+
+app.use(trimTrailingSlash())
+app.get('/about/me', (c) => c.text('Without Trailing Slash'))
+```
+
+## Note
+
+It will be enabled when the request method is `GET` and the response status is `404`.