Add getting started samples file
user
```ruby
require "aws_iot_device"

host = "AWS IoT endpoint"
port = 8883
thing = "Thing Name"
root_ca_path = "Path to your CA certificate"
private_key_path = "Path to your private key"
certificate_path = "Path to your certificate"

shadow_client = AwsIotDevice::MqttShadowClient::ShadowClient.new
shadow_client.configure_endpoint(host, port)
shadow_client.configure_credentials(root_ca_path, private_key_path, certificate_path)
shadow_client.create_shadow_handler_with_name(thing, true)

shadow_client.connect
shadow_client.get_shadow do |message|
  # Do what you want with the get_shadow's answer
  p ":)"
end
sleep 2 #Timer to ensure that the answer is received

shadow_client.disconnect
```
assistant