Add robots meta tags on pages in robots.txt

Useful when app is at a non-root path and we're not handling top-level
/robots.txt requests.

app/templates/followers.html

@@ -3,6 +3,7 @@
 
 {% block head %}
 <title>{{ local_actor.display_name }}'s followers</title>
+<meta name="robots" content="noindex, nofollow">
 {% endblock %}
 
 {% block content %}