Add banner and updated ReadMe (#33)

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README.md

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-# Terraform AWS VPN
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+<a href="https://www.appvia.io/"><img src="./appvia_banner.jpg" alt="Appvia Banner"/></a><br/><p align="right"> <a href="https://registry.terraform.io/modules/appvia/vpn/aws/latest"><img src="https://img.shields.io/static/v1?label=APPVIA&message=Terraform%20Registry&color=191970&style=for-the-badge" alt="Terraform Registry"/></a></a> <a href="https://github.com/appvia/terraform-aws-vpn/releases/latest"><img src="https://img.shields.io/github/release/appvia/terraform-aws-vpn.svg?style=for-the-badge&color=006400" alt="Latest Release"/></a> <a href="https://appvia-community.slack.com/join/shared_invite/zt-1s7i7xy85-T155drryqU56emm09ojMVA#/shared-invite/email"><img src="https://img.shields.io/badge/Slack-Join%20Community-purple?style=for-the-badge&logo=slack" alt="Slack Community"/></a> <a href="https://github.com/appvia/terraform-aws-vpn/graphs/contributors"><img src="https://img.shields.io/github/contributors/appvia/terraform-aws-vpn.svg?style=for-the-badge&color=FF8C00" alt="Contributors"/></a> 
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+# Description
 
 This repository creates an AWS Client VPN Endpoint for the AWS Organization, which is connected to the AWS Transit Gateway.