Document network gateway components and configuration

Description

• Diagram to explain different software components and network interfaces for a client setup
• Diagram to explain different software components and network interfaces for a gateway setup
• Describe the used software components and the key functionality we use them for
• Describe the subnet address handling for IPv4 as well as IPv6
• Describe the currently supported connectivity technologies (Ethernet, Wi-Fi, Thread, etc)
• Describe provisioning and configuration options for users (e.g. SoftAP, static network config provisioning, etc)