Title: Envoy documentation should be Windows-friendly

Description:

Various code snippets and configuration files in the documentation (https://www.envoyproxy.io/docs/envoy/latest/start/start) rely on POSIX tools (e.g. chown) and primitives such as /dev/null/.

As we make progress towards #129, we should revisit the documentation experience for Windows users.

As we do this work, we need to consider documentation bloat. We should try to avoid duplicating every example and code snippet for Windows as it would make the documentation harder to maintain.

PowerShell on Windows offers aliases for many of the commonly used POSIX commands so we could possibly leverage it.

cc @envoyproxy/windows-dev