Add Set The Default Development Port as a Rails til

rails/set-the-default-development-port.md

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+# Set The Default Development Port
+
+For Rails 5+, Puma has been the default web server that gets installed with new
+Rails apps. Puma comes with some configuration in the `config/puma.rb` file.
+
+If you open that file up, you'll see a number of settings that can be
+configured. One of them is the `port` that `puma` uses.
+
+```ruby
+# Specifies the `port` that Puma will listen on to receive requests; default is 3000.
+#
+port        ENV.fetch('PORT') { 3000 }
+```
+
+It looks for a `PORT` value in the envionrment and uses that if it is present.
+That means you could run:
+
+```bash
+PORT=5005 rails s
+```
+
+and Puma would server the local development server at `localhost:5005`. If that
+value is not present, it will fallback to `#fetch`'s block which contains
+`3000`.
+
+If you always want to local Rails development server to run at a port other
+than `3000`, all you need to do is update that line.
+
+```ruby
+port        ENV.fetch('PORT') { 5005 }
+```
+
+Now, running `rails s` on its own will start the dev server up at
+`localhost:5005`.
+
+[source](https://schneems.com/2017/03/13/puma-ports-and-polish/)