[derpibooru] add search and gallery extractors (#862)

docs/configuration.rst

@@ -696,6 +696,34 @@ Description
     * ``false``: Converted video files
 
 
+extractor.derpibooru.api-key
+----------------------------
+Type
+    ``string``
+Default
+    ``null``
+Description
+    Your `Derpibooru API Key <https://derpibooru.org/registrations/edit>`__,
+    to use your account's browsing settings and filters.
+
+
+extractor.derpibooru.filter
+---------------------------
+Type
+    ``integer``
+Default
+    ``null``
+Example
+    ``56027`` (`Everything <https://derpibooru.org/filters/56027>`_ filter)
+Description
+    The content filter ID to use.
+
+    Setting an explicit filter ID overrides any default filters and can be used
+    to access 18+ content without `API Key <extractor.derpibooru.api-key_>`_.
+
+    See `Filters <https://derpibooru.org/filters>`_ for details.
+
+
 extractor.deviantart.extra
 --------------------------
 Type

docs/supportedsites.rst

@@ -22,6 +22,7 @@ baraag               https://baraag.net/                 Images from Statuses, U
 Behance              https://www.behance.net/            Collections, Galleries, User Profiles
 Blogger              https://www.blogger.com/            Blogs, Posts, Search Results
 Danbooru             https://danbooru.donmai.us/         Pools, Popular Images, Posts, Tag Searches         Supported
+Derpibooru           https://derpibooru.org/             Galleries, Posts, Search Results                   `API Key <configuration.rst#extractorderpibooruapi-key>`__
 Desuarchive          https://desuarchive.org/            Boards, Search Results, Threads
 DeviantArt           https://www.deviantart.com/         |deviantart-C|                                     `OAuth <https://github.com/mikf/gallery-dl#oauth>`__
 Doki Reader          https://kobato.hologfx.com/reader/  Chapters, Manga