Allow for views to supply tags to header

src/views/error.ecr

@@ -1,4 +1,5 @@
 <% content_for "header" do %>
-<%= "Error - " %>
+<title><%= "Error" %> - Invidious</title>
 <% end %>
+
 <%= error_message %>

src/views/index.ecr

@@ -1,2 +1,3 @@
 <% content_for "header" do %>
+<title>Invidious</title>
 <% end %>