How to create custom view fields programmatically: Unfiltered header area field and content field plugins

If you ever tried to add custom styles or custom javascript to Unfiltered text field in Drupal 8 view, you had probably noticed that the style/script tags are always stripped out. Here is the example of how to programmatically create the unfiltered view header area custom field and the unfiltered view content field plugins where you can use <style> or <script> tags.