rails-new: add page (#15607)

pages/common/rails-new.md

@@ -0,0 +1,24 @@
+# rails new
+
+> Create a new Rails application.
+> More information: <https://guides.rubyonrails.org/command_line.html#rails-new>.
+
+- Create a Rails app named `blog` in the current directory:
+
+`rails new blog`
+
+- Create a Rails app with API-only configuration:
+
+`rails new {{app_name}} --api`
+
+- Create a Rails app with `postgresql` as the database:
+
+`rails new {{app_name}} --database postgresql`
+
+- Create a Rails app without generating JavaScript files:
+
+`rails new {{app_name}} --skip-javascript`
+
+- Display help:
+
+`rails new --help`