[Docs] Add cookbook for exposing a 404 page

.editorconfig

@@ -17,7 +17,7 @@ indent_style = space
 indent_size = 4
 
 [*.md]
-max_line_length = 80
+max_line_length = 120
 trim_trailing_whitespace = false
 
 [*.js]

README.md

@@ -70,5 +70,6 @@ Stenope is not a ready-to-use bloging system: but you could quickly _write your
 <!-- TODO - [Adding custom files to the build]() -->
 <!-- TODO - [Data source: writing a custom Provider]() -->
 <!-- TODO - [Data format: writing a custom Decoder]() -->
-- [Data manipulation: writing a custom Processor](doc/processors.md)
+- [Data manipulation: writing a custom Processor](doc/cookbooks/processors.md)
+- [Exposing a not found page](doc/cookbooks/not-found-page.md)
 <!-- TODO - [How to automatically deploy and host a static site]() -->

doc/app/src/Controller/DocController.php

@@ -25,7 +25,7 @@ public function index()
         return $this->render('doc/index.html.twig', ['page' => $page]);
     }
 
-    #[Route('/{page}', name: 'page')]
+    #[Route('/{page<.+>}', name: 'page')]
     public function page(Page $page)
     {
         return $this->render('doc/page.html.twig', ['page' => $page]);

doc/cookbooks/not-found-page.md

@@ -0,0 +1,57 @@
+# Exposing a not found page
+
+Since Stenope is a static site generator, it does not handle 404 errors for missing pages.
+Instead, your web server should handle them.
+
+However, you can let Stenope generate a 404.html page for you, and let your web server serve it.
+
+For instance, add in your `config/routes.yaml`:
+
+```yaml
+errors_404:
+    path: 404.html
+    controller: Symfony\Bundle\FrameworkBundle\Controller\TemplateController
+    defaults:
+        template: errors/404.html.twig
+    options:
+        stenope:
+            sitemap: false
+```
+
+and create the `templates/errors/404.html.twig` template:
+
+```twig
+{% extends 'base.html.twig' %}
+
+{% block title %}Page not found{% endblock %}
+
+{% block content %}
+    <h1>404 Not Found</h1>
+    
+    <p>The page you are looking for does not exist.</p>
+{% endblock %}
+```
+
+Then, configure your web server to serve this page when a 404 error occurs.
+
+Nginx:
+
+```nginx
+server {
+    # […]
+    
+    location / {
+        try_files $uri $uri/index.html =404;
+    }
+    location ~ \.html {
+        internal;
+    }
+    
+    error_page 404 /404.html;
+```
+
+Apache:
+
+```apacheconf
+ErrorDocument 404 /404.html
+```