Fix some things, urlencode post names

the jinja2 function urlencode is apparently not implemented :(

src/file.ml

@@ -1,7 +1,10 @@
 open Yocaml
 
 let is_css = with_extension "css"
-let is_javascript = with_extension "js"
+let is_javascript =
+  let open Preface.Predicate in
+  with_extension "js" ||
+  with_extension "map"
 
 let is_image =
   let open Preface.Predicate in

src/model.ml

@@ -45,7 +45,7 @@ module Article = struct
          make
          <$> V.(required_assoc string) "title" assoc
          <*> V.(required_assoc (Metadata.Date.from (module V))) "date" assoc
-         <*> V.(required_assoc (Author.from (module V))) "author" assoc)
+         <*> V.(optional_assoc_or (Author.from (module V))) "author" assoc ~default:Author.default_author)
       obj
 
   let from_string (module V : Metadata.VALIDABLE) = function

src/task.ml

@@ -28,7 +28,7 @@ let move_images target =
 let move_js target =
   process_files
     [ "js" ]
-    (fun f -> File.is_javascript f || with_extension "map" f)
+    File.is_javascript
     (Build.copy_file ~into:(js_target target))
 
 let move_audio target =
@@ -71,7 +71,7 @@ let process_articles target =
 let articles =
   let open Build in
   collection
-    (read_child_files "posts" (with_extension "md"))
+    (read_child_files "posts" File.is_markdown)
     (fun path ->
        Metaformat.read_file_with_metadata (module Model.Article) path
        >>^ fun (meta, _data) ->