code: function replaceEnvironmentVariables (fileContent) {
    const environmentVariable = new RegExp(/\${([^}]+)}/g)
    // eslint-disable-next-line
    fileContent = fileContent.replace(environmentVariable, (a, b) => process.env[b] || '')
    return fileContent
  }
docs: Handle the introduction of global enviroment variables within
  the yml file, allowing value substitution.
  
  For example:
  ```
  host: $HOST_NAME
  port: $HOST_PORT
  ```
  
  @param {String} fileContent The loaded yml file
  
  @private
  @returns {void}