Add automatic environment variable loading and Variables in yml config.

[tanema]

Features

This PR encapsulates 2 main features.

• Automatically load environment variables from a file during runtime
• Allow environment variable interpolation in the config

This will allow developers to much more easily commit their code to public repos without revealing their passwords or their clients.

Environment variable loading

The normal user configuration paths are used so depending on OS the path used would be:
Windows: %APPDATA%\Shopify\Themekit\variables
Linux/BSDs: ${XDG_CONFIG_HOME}/Shopify/Themekit/variables
MacOSX: ${HOME}/Library/Application Support/Shopify/Themekit/variables

Themekit will also look for a variables file within the project directory. There has also been a flag added --vars will provide a path to a variables file.

The format of these files would look like a normal .env file:

DEV_PASSWD=0bwef09hn23048sdkl2345n2k3

Config file interpolation.

The config looks would like this:

development:
  password: ${DEV_PASSWD}
  theme_id: ${DEV_THEMEID}
  store: ${DEV_SHOP}

and the commands can be run as normal. This will not add any breaking functionality and should not break any existing workflows

Warn Checklist

• This changes the interface and requires a Major/Minor version change.
• I have 🎩'd these changes by using the commands I changed by hand.
• I have added a dependancy to the project.

[tanema]

use https://github.com/shibukawa/configdir for finding the config dir
use https://github.com/alexsasharegan/dotenv for loading a dotenv file