Add wsl2 support for warden

[ihor-sviziev]

Fixes #212

As a workaround now we can add following lines in order to have working xdebug with warden on WSL2:

XDEBUG_CONNECT_BACK_HOST=host.docker.internal
WARDEN_ENV_DEBUG_HOST=host.docker.internal

After this change warden debug works fine without adding any new params to .env file.

this is retrieved from wsl2:

$ echo "$(< /proc/sys/kernel/osrelease)"
4.19.104-microsoft-standard

[davidalger]

Very nice, thank you! I tweaked the checks a bit to be case-insensitive using grep to avoid an error on Darwin/MacOS where /proc files do not exist:

/opt/warden/commands/env.cmd: line 32: /proc/sys/kernel/osrelease: No such file or directory

Verified this is working as expected on WSL2, Darwin, Linux via following checks:

warden debug -c 'printenv XDEBUG_REMOTE_HOST'
warden env exec nginx grep HTTP_X_DEBUG_HOST /etc/nginx/fastcgi_params

On WSL2 and Darwin both are host.docker.internal as expected and neither contain that value on Fedora Linux (as expected).

Going to get this merged and tag a release here shortly. Thanks for the contribution @ihor-sviziev!