DEV: enable frozen string literal on all files

This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.

Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging

lib/freedom_patches/sprockets_patches.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This contains two patches to make sprockets more tolerable in dev
 #
 # 1. Stop computing asset paths which triggers sprockets to do mountains of work