Add titles to research articles

app/views/research/index.html.erb

@@ -5,16 +5,19 @@
 <div class="container px-5 my-5">
   <div class="row gx-5 justify-content-center">
     <div class="grid-container download-container">
+      <h2 class="my-3 text-center fs-5">Test anxiety and poor sleep: a vicious cycle</h2>
       <%= link_to(research_download_pdf_path(path: "test_anxiety_and_poor_sleep")) do  %>
         <%= image_tag "research/test_anxiety_and_sleep.png", class: "file-download"  %>
       <% end %>
     </div>
     <div class="grid-container download-container">
+      <h2 class="my-3 text-center fs-5">The psychological toll of high-stakes testing</h2>
       <%= link_to(research_download_pdf_path(path: "psychological_toll_of_high_stakes_testing")) do  %>
         <%= image_tag "research/psychological_toll_of_high_stakes_testing.png", class: "file-download"  %>
       <% end %>
     </div>
     <div class="grid-container download-container">
+      <h2 class="my-3 text-center fs-5">Testing, stress, and performance: How students respond phycologically to high-stakes testing</h2>
       <%= link_to(  research_download_pdf_path(path: "testing_stress_and_performance")) do  %>
         <%= image_tag "research/testing_stress.png", class: "file-download"  %>
       <% end %>