Add DefGuard to VPN (#559)

README.md

@@ -699,6 +699,7 @@ Virtualization software.
 
 VPN software.
 
+- [DefGuard](https://defguard.net/) - True enterprise WireGuard with MFA/2FA and SSO. ([Source Code](https://github.com/DefGuard)) `Apache-2.0` `Rust`
 - [Dockovpn](https://dockovpn.io) - Out-of-the-box stateless dockerized OpenVPN server which starts in less than 2 seconds. ([Source Code](https://github.com/dockovpn/dockovpn)) `GPL-2.0` `Docker`
 - [Firezone](https://www.firez.one/) - WireGuard based VPN Server and Firewall. ([Source Code](https://github.com/firezone/firezone)) `Apache-2.0` `Docker`
 - [Headscale](https://github.com/juanfont/headscale) - Self-hostable fork of [Tailscale](https://tailscale.com), cross-platform clients, simple to use, built-in (currently experimental) monitoring tools. `BSD-3-Clause` `Go`