[mastodon] Add Support for Videos (#51)

It is now possible to play videos from toots within FeedDeck. For that
we are using the "madia_kit" package, which is already used for the
Podcast player on Windows and Linux.

The videos from a toot are saved within the "options.videos" field of an
item next to the "options.media" field. In the "ItemDetailsMastodon"
widget we are then checking if this field is present and contains a list
of video urls. These urls can then be played via the "ItemVideos"
widget.

app/linux/flutter/generated_plugin_registrant.cc

@@ -7,6 +7,7 @@
 #include "generated_plugin_registrant.h"
 
 #include <media_kit_libs_linux/media_kit_libs_linux_plugin.h>
+#include <media_kit_video/media_kit_video_plugin.h>
 #include <screen_retriever/screen_retriever_plugin.h>
 #include <url_launcher_linux/url_launcher_plugin.h>
 #include <window_manager/window_manager_plugin.h>
@@ -15,6 +16,9 @@ void fl_register_plugins(FlPluginRegistry* registry) {
   g_autoptr(FlPluginRegistrar) media_kit_libs_linux_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "MediaKitLibsLinuxPlugin");
   media_kit_libs_linux_plugin_register_with_registrar(media_kit_libs_linux_registrar);
+  g_autoptr(FlPluginRegistrar) media_kit_video_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "MediaKitVideoPlugin");
+  media_kit_video_plugin_register_with_registrar(media_kit_video_registrar);
   g_autoptr(FlPluginRegistrar) screen_retriever_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "ScreenRetrieverPlugin");
   screen_retriever_plugin_register_with_registrar(screen_retriever_registrar);

app/linux/flutter/generated_plugins.cmake

@@ -4,6 +4,7 @@
 
 list(APPEND FLUTTER_PLUGIN_LIST
   media_kit_libs_linux
+  media_kit_video
   screen_retriever
   url_launcher_linux
   window_manager