add Dockerfile and configure production app

config/puma.rb

@@ -6,7 +6,7 @@
 # the maximum value specified for Puma. Default is set to 5 threads for minimum
 # and maximum; this matches the default thread size of Active Record.
 #
-max_threads_count = ENV.fetch('RAILS_MAX_THREADS', 10)
+max_threads_count = ENV.fetch('RAILS_MAX_THREADS', 15)
 min_threads_count = ENV.fetch('RAILS_MIN_THREADS') { max_threads_count }
 threads min_threads_count, max_threads_count
 
@@ -24,7 +24,7 @@ port ENV.fetch('PORT', 3000)
 environment ENV.fetch('RAILS_ENV', 'development')
 
 # Specifies the `pidfile` that Puma will use.
-pidfile ENV.fetch('PIDFILE', 'tmp/pids/server.pid')
+# pidfile ENV.fetch('PIDFILE', 'tmp/pids/server.pid')
 
 # Specifies the number of `workers` to boot in clustered mode.
 # Workers are forked web server processes. If using threads and workers together