GitHub App announcement (#12280)

Show a message in the dashboard to promote GitHub App.

Requires: readthedocs/ext-theme#619
Closes: readthedocs/ext-theme#616

Author: humitos

readthedocs/projects/views/private.py

@@ -119,6 +119,8 @@ def get_context_data(self, **kwargs):
             n_projects < 3 and (timezone.now() - projects.first().pub_date).days < 7
         ):
             template_name = "example-projects.html"
+        elif n_projects and not settings.RTD_ALLOW_ORGANIZATIONS:
+            template_name = "github-app.html"
         elif n_projects and not projects.filter(external_builds_enabled=True).exists():
             template_name = "pull-request-previews.html"
         elif n_projects and not projects.filter(addons__analytics_enabled=True).exists():