Add language for blog

src/gloss/config.gleam

@@ -46,6 +46,7 @@ pub type Configuration {
   Configuration(
     blog_name: String,
     blog_url: String,
+    language: String,
     author: Author,
     compiling: Compiling,
     rendering: Rendering,

src/gloss/defaults.gleam

@@ -22,12 +22,14 @@ const default_views = config.Views(
 pub fn default_config(
   blog_name: String,
   blog_url: String,
+  language: String,
   author: config.Author,
   copyright: String,
 ) -> Configuration {
   Configuration(
     blog_name: blog_name,
     blog_url: blog_url,
+    language: language,
     author: author,
     compiling: Compiling(
       database_compiler: compiler.compile,

src/gloss/rendering/views/base.gleam

@@ -49,7 +49,7 @@ fn view(
     prefix -> prefix <> " · " <> config.blog_name
   }
 
-  html([], [
+  html([attribute("lang", config.language)], [
     head([], [
       meta([attribute("charset", "utf-8")]),
       meta([