Document how to colorize dry-cli output

docsite/source/colorizing-your-output.html.md

@@ -0,0 +1,55 @@
+---
+title: Colorizing your output
+layout: gem-single
+name: dry-cli
+---
+
+`dry-cli` comes with some functions to help you print colored text in the terminal. The program bellow demonstrate all available functions:
+
+```ruby
+#!/usr/bin/env ruby
+require "bundler/setup"
+require "dry/cli"
+
+module ColorsDemo
+  extend Dry::CLI::Registry
+
+  class Print < Dry::CLI::Command
+    desc "Demonstrate all available colors"
+
+    def call
+      demo = <<~DEMO
+        # Style ###############################################################
+        Bold: #{bold("This is bold")}
+        # Foreground ##########################################################
+        Black:   #{black("This is black")}
+        Red:     #{red("This is red")}
+        Green:   #{green("This is green")}
+        Yellow:  #{yellow("This is yellow")}
+        Blue:    #{blue("This is blue")}
+        Magenta: #{magenta("This is magenta")}
+        Cyan:    #{cyan("This is cyan")}
+        White:   #{white("This is white")}
+        # Background ##########################################################
+        Black:   #{on_black("This is black")}
+        Red:     #{on_red("This is red")}
+        Green:   #{on_green("This is green")}
+        Yellow:  #{on_yellow("This is yellow")}
+        Blue:    #{on_blue("This is blue")}
+        Magenta: #{on_magenta("This is magenta")}
+        Cyan:    #{on_cyan("This is cyan")}
+        White:   #{on_white("This is white")}
+        # Combinations ########################################################
+        Bold+Foreground:            #{bold(red("This is bold red"))}
+        Bold+Background:            #{bold(on_green("This is bold on green"))}
+        Bold+Foreground+Background: #{bold(red(on_green("This is bold red on green")))}
+      DEMO
+      puts demo
+    end
+  end
+
+  register "print", Print
+end
+
+Dry.CLI(ColorsDemo).call
+```

docsite/source/index.html.md

@@ -12,6 +12,7 @@ sections:
   - variadic-arguments
   - commands-with-subcommands-and-params
   - callbacks
+  - colorizing-your-output
 ---
 
 `dry-cli` is a general-purpose framework for developing Command Line Interface (CLI) applications. It represents commands as objects that can be registered and offers support for arguments, options and forwarding variadic arguments to a sub-command.