[mangadex] document 'metadata' and 'lang' options (#1535)

docs/configuration.rst

@@ -771,6 +771,7 @@ Description
     * ``true``: Original ZIP archives
     * ``false``: Converted video files
 
+
 extractor.danbooru.metadata
 ---------------------------
 Type
@@ -782,6 +783,7 @@ Description
 
     Note: This requires 1 additional HTTP request for each post.
 
+
 extractor.derpibooru.api-key
 ----------------------------
 Type
@@ -1244,6 +1246,27 @@ Description
     The server to use for API requests.
 
 
+extractor.mangadex.lang
+-----------------------
+Type
+    ``string``
+Example
+    ``"en"``
+Description
+    `ISO 639-1 <https://en.wikipedia.org/wiki/ISO_639-1>`_ language code
+    to filter chapters by.
+
+
+extractor.mangadex.metadata
+---------------------------
+Type
+    ``bool``
+Default
+    ``false``
+Description
+    Provide ``artist``, ``author``, and ``group`` metadata fields.
+
+
 extractor.newgrounds.flash
 --------------------------
 Type

docs/gallery-dl.conf

@@ -148,7 +148,9 @@
         },
         "mangadex":
         {
-            "api-server": "https://api.mangadex.org"
+            "api-server": "https://api.mangadex.org",
+            "metadata": false,
+            "lang": null
         },
         "mangoxo":
         {