Include image description in status media cards

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

changelog.d/card-image-description.add

@@ -0,0 +1 @@
+Include image description in status media cards

lib/pleroma/web/api_spec/schemas/status.ex

@@ -58,6 +58,10 @@ defmodule Pleroma.Web.ApiSpec.Schemas.Status do
             format: :uri,
             description: "Preview thumbnail"
           },
+          image_description: %Schema{
+            type: :string,
+            description: "Alternate text that describes what is in the thumbnail"
+          },
           title: %Schema{type: :string, description: "Title of linked resource"},
           description: %Schema{type: :string, description: "Description of preview"}
         }

lib/pleroma/web/mastodon_api/views/status_view.ex

@@ -583,6 +583,7 @@ def render("card.json", %Card{fields: rich_media}) do
       provider_url: page_url_data.scheme <> "://" <> page_url_data.host,
       url: page_url,
       image: image_url,
+      image_description: rich_media["image:alt"] || "",
       title: rich_media["title"] || "",
       description: rich_media["description"] || "",
       pleroma: %{