Add types for actiontext v8.1

gems/actiontext/8.1/_test/metadata.yaml

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+additional_gems:
+  - activerecord

gems/actiontext/8.1/_test/test.rb

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+require "actiontext"
+
+class Article < ActiveRecord::Base
+  has_rich_text :content
+end
+
+class Comment < ActiveRecord::Base
+  has_rich_text :body, store_if_blank: false
+end
+
+ActionView::Helpers::FormBuilder.new(:article, Article.new, ActionView::Base.empty, {}).rich_textarea(:content, class: "editor")
+ActionText::Content.render(partial: "action_text/contents/content")
+ActionText::Attachment.fragment_by_minifying_attachments("<p>text</p>")
+
+rich_text = ActionText::RichText.new
+rich_text.name.to_sym
+rich_text.body&.to_html
+rich_text.embeds.attached?
+rich_text.updated_at.to_date
+rich_text.to_s.size
+rich_text.to_plain_text.size
+rich_text.to_trix_html&.size
+if (content = rich_text.body)
+  content.links.first&.size
+  content.attachments.first&.to_html
+  content.gallery_attachments.size
+  content.to_plain_text.size
+  content.to_trix_html.size
+  content.to_html.size
+  content.to_s.size
+end

gems/actiontext/8.1/_test/test.rbs

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+class Article < ActiveRecord::Base
+end
+
+class Comment < ActiveRecord::Base
+end