Add bilingual French/English support with Hugo multilingual config

Configure Hugo multilingual mode (fr default, en secondary) with
Hextra's language-switch menu entry, and translate all existing
content pages to English using Hugo's per-file language suffix
convention (.en.md alongside .fr.md).

hugo.yaml

@@ -3,7 +3,16 @@ title: 🧑‍💻 Notebook
 theme: hextra
 
 defaultContentLanguage: fr
-locale: fr
+
+languages:
+  fr:
+    label: Français
+    locale: fr-FR
+    weight: 1
+  en:
+    label: English
+    locale: en-US
+    weight: 2
 
 menu:
   main:
@@ -23,8 +32,13 @@ menu:
       weight: 5
       params:
         type: search
-    - name: Gitea
+    - name: Language
       weight: 6
+      params:
+        type: language-switch
+        label: true
+    - name: Gitea
+      weight: 7
       url: "https://gitea.arnodo.fr/Damien"
       params:
         icon: gitea