[FEATURE REQUEST] Env variables for services

[butschster]

It would be great to have ability to set ENV variables for each service.

Something like this:

service:
  monolog:
    command: "php artisan monolog:start --host=0.0.0.0 --port=9913"
    process_num: 1
    exec_timeout: 0
    restart_sec: 1
    line_ending: ""
    env:
      TERM_PROGRAM: Hyper
  var-dumper:
    command: "php artisan var-dumper:start --host=0.0.0.0 --port=9912"
    process_num: 1
    exec_timeout: 0
    restart_sec: 1
    line_ending: ""
    env:
      FOO: BAR