Change product title from h1 to h2

[spencercanner]

• Change product title element from h1 to h2
• Although we're not aware of the context in which buy buttons are embedded, semantically the product title should most likely not be an h1
  • This can always be configured by the consumer by customizing the product title template
• In the case of collections, we end up having a bunch of h1 elements which can make it difficult to parse the page when using a screen reader
• This change also applies to the modal product title

To 🎩 :

• Create a buy button with a button destination of modal
• Navigate a virtual cursor to the product title
• Verify that it is announced as a heading level 2
• Open the product details modal
• Navigate a virtual cursor to the modal product title
• Verify that it is announced as a heading level 2
• Sanity check that styling is unaffected by the tag change

• Chrome, Firefox, Safari (Sanity check)
• Safari/Mac VoiceOver
• Firefox/Windows NVDA