docs: Add instance private IP in the outputs section

Author: Mustafa Mujahid

README.md

@@ -246,6 +246,7 @@ No modules.
 | <a name="output_password_data"></a> [password\_data](#output\_password\_data) | Base-64 encoded encrypted password data for the instance. Useful for getting the administrator password for instances running Microsoft Windows. This attribute is only exported if `get_password_data` is true |
 | <a name="output_primary_network_interface_id"></a> [primary\_network\_interface\_id](#output\_primary\_network\_interface\_id) | The ID of the instance's primary network interface |
 | <a name="output_private_dns"></a> [private\_dns](#output\_private\_dns) | The private DNS name assigned to the instance. Can only be used inside the Amazon EC2, and only available if you've enabled DNS hostnames for your VPC |
+| <a name="output_private_ip"></a> [private\_ip](#output\_private\_ip) | The private IP address assigned to the instance, if applicable. |
 | <a name="output_public_dns"></a> [public\_dns](#output\_public\_dns) | The public DNS name assigned to the instance. For EC2-VPC, this is only available if you've enabled DNS hostnames for your VPC |
 | <a name="output_public_ip"></a> [public\_ip](#output\_public\_ip) | The public IP address assigned to the instance, if applicable. NOTE: If you are using an aws\_eip with your instance, you should refer to the EIP's address directly and not use `public_ip` as this field will change after the EIP is attached |
 | <a name="output_spot_bid_status"></a> [spot\_bid\_status](#output\_spot\_bid\_status) | The current bid status of the Spot Instance Request |