Update zola to 0.14.1 and fix doc search

Issue: #1120

website/site/config.toml

@@ -4,14 +4,14 @@ base_url = "https://docspell.org"
 # Whether to automatically compile all Sass files in the sass directory
 compile_sass = true
 
-[markdown]
-# Whether to do syntax highlighting
-# Theme can be customised by setting the `highlight_theme` variable to a theme supported by Zola
-highlight_code = true
-highlight_theme = "gruvbox-dark"
 
 # Whether to build a search index to be used later on by a JavaScript library
 build_search_index = true
+default_language = "en"
+
+[markdown]
+highlight_code = true
+highlight_theme = "gruvbox-dark"
 
 [link_checker]
 skip_prefixes = [