Merge pull request #1665 from cisagov/cd/preload-email

Issue #895: Add preload content to status_change_approved.txt

src/registrar/templates/emails/status_change_approved.txt

@@ -32,6 +32,14 @@ Learn more about:
 - Domain security best practices <https://get.gov/domains/security/> 
 
 
+WE’LL PRELOAD THIS DOMAIN
+We add new .gov domains to the HSTS preload list each month. This requires browsers to use a secure HTTPS connection to any website at this domain and ensures the content you publish is exactly what your visitors get. It also means you’ll need to support HTTPS anywhere the domain is used for websites – on the internet or internally. We’ll add your domain to the preload list soon.
+
+Learn more about:
+- What preloading is <https://get.gov/domains/security/#preload-your-domain>
+- Why we preload new domains <https://get.gov/posts/2021-06-21-an-intent-to-preload/>
+
+
 THANK YOU
 .Gov helps the public identify official, trusted information. Thank you for using a .gov domain.