French translation for docs (#3030)

original PR go-gitea/docs#147 and author @0xbaadf00d

docs/docker/caddy.conf

@@ -1,7 +1,7 @@
 :80 {
   root /srv/www
 
-  locale en-US zh-CN zh-TW pt-BR nl-NL {
+  locale en-US zh-CN zh-TW pt-BR nl-NL fr-FR {
     detect header
   }
 
@@ -35,5 +35,10 @@
     to /nl-nl/{1}
   }
 
+  rewrite /fr-FR/ {
+    regexp (.*)
+    to /fr-fr/{1}
+  }
+
   header / Vary "Accept-Language"
 }