Extract components to edit and add cards

This way we'll be able to reuse it in the SDG Management section while
reusing the `title` method to set the page title.

app/components/admin/widget/cards/edit_component.rb

@@ -0,0 +1,19 @@
+class Admin::Widget::Cards::EditComponent < ApplicationComponent
+  include Header
+  attr_reader :card, :index_path
+
+  def initialize(card, index_path:)
+    @card = card
+    @index_path = index_path
+  end
+
+  private
+
+    def title
+      if card.header?
+        t("admin.homepage.edit.header_title")
+      else
+        t("admin.homepage.edit.card_title")
+      end
+    end
+end