#7088363 Emails: Add email forwarding and support links to In-Depth Comparison page

This pull request updates the In-Depth Comparison page to show a link to the support page for each email provider. It also adds a link in the footer to present the Email Forwarding option to users:

Desktop	Mobile

Testing instructions

Note you will have to append ?flags=emails/in-depth-comparison to the url of the page (and reload it) if you’re testing those changes on a live branch as this feature has not been enabled on this environment yet:

1. Run git checkout update/in-depth-comparison-page and start your server, or access a live branch
2. Log into a WordPress.com account with a domain but no email
3. Open the Emails page
4. Click the Add Email button of that domain to access the Email Comparison page
5. Click the See how they compare link to access the In-Depth Comparison page
6. Assert that the Learn more links open the right support pages on desktop and mobile
7. Assert that the Email Forwarding link opens the Add New Email Forwards page on desktop and mobile