Restore license setup guidance in initializer comments

Over-trimmed in the previous cleanup commit. The longer wording has
non-obvious info (where to get the JWT, which envs skip license,
what Pro does when no license is set) that readers genuinely benefit
from — beyond what the generator template's one-line version captures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ihabadham

config/initializers/react_on_rails_pro.rb

@@ -1,7 +1,9 @@
 # frozen_string_literal: true
 
 # See https://reactonrails.com/docs/configuration/configuration-pro
-# License: Set REACT_ON_RAILS_PRO_LICENSE environment variable
+# Production license: set REACT_ON_RAILS_PRO_LICENSE to the JWT token from
+# https://pro.reactonrails.com/. Development and test environments don't
+# require a license — the Pro engine logs an info-level notice only.
 ReactOnRailsPro.configure do |config|
   config.server_renderer = "NodeRenderer"
   # Raise loudly when the renderer is unavailable instead of silently