Summary: Dub adds Email Campaigns

Why It Matters: This change shows Dub is adding new ways for users to reach customers.

What Changed:

• A new blog post link "Introducing Email Campaigns" was added to the main page.
• The changelog now lists "Introducing Email Campaigns" as a new feature.
• The "Introducing Dub Partners" blog post link was removed from the main page.
• The "Log in" and "Sign Up" links moved to a different spot at the top of the page.
• Some customer case study images were rearranged.
• Code blocks were added around the SDK examples.