add explicit test for site.data.authors[author] as a string

spec/jekyll_seo_tag/drop_spec.rb

@@ -240,6 +240,15 @@ RSpec.describe Jekyll::SeoTag::Drop do
         end
       end
 
+      context "with site.authors[author] as string" do
+        let("data") { { "authors" => { "foo" => "bar" } } }
+        let(:page_meta) { {"author" => "foo"} }
+
+        it "doesn't error" do
+          expect(subject.author).to eql({"name"=>"foo", "twitter"=>"foo"})
+        end
+      end
+
       %i[with without].each do |site_data_type|
         context "#{site_data_type} site.author data" do
           let(:data) do