Respect environment when defined as part of build command

[chrissealey]

Currently—from what I can tell—this plugin is only using the environment defined by Jekyll's config file. It is possible to set an environment as part of your command with JEKYLL_ENV=production; removing the need to change config as you go from development to production, etc.

More information here:
https://jekyllrb.com/docs/configuration/#build-command-options

[captn3m0]

As a workaround, I'm currently using 2 config files. _config.yml includes env: development, so default jekyll build works as normal (with the plugin disabled).

For prod builds, I have a second prod.yml, which contains env: production. I run the build as JEKYLL_ENV=production jekyll build --config _config.yml,prod.yml to override the environment.

Ideally, the plugin should be disabled on development (default), and only run on production environments, with perhaps a configuration option to list the environments where the plugin should run.