Map caps lock to l_control when used as modifier and esc when alone

karabiner.json

{
  "profiles": [
    {
      "name": "Default profile",
      "selected": true,
      "complex_modifications": {
        "rules": [
          {
            "description": "A Modern Space Cadet (Steve Losh)",
            "manipulators": [
              {
                "type": "basic",
                "from": {"key_code": "caps_lock"},
                "to": [{"key_code": "left_control"}],
                "to_if_alone": [{"key_code": "escape"}]
              }
  	    ]
          }
        ]
      }
    }
  ]
}