The workflow visibility seems affected when adding bootstrap CSS

[sbruyere]

Description:
When incorporating the workflow graph as a web component and adding Bootstrap CSS to the demo page, the visibility of the workflow is compromised. This issue arises due to the external CSS affecting the styling of the workflow graph.

To Reproduce:

1. Integrate the workflow graph as a web component.
2. Add the following line to the section of the demo page:

<link rel="stylesheet" href="css/bootstrap/bootstrap.min.css" />

7. Observe how it impacts the visibility of the workflow.

Proposed Solution:
Implement a Shadow DOM mechanism to encapsulate the styling of the workflow graph, ensuring that it remains unaffected by external CSS styles. This will enhance the reliability and consistency of the workflow's appearance across different environments.

This enhancement would greatly benefit users who rely on the workflow graph within web components, ensuring seamless integration without interference from external stylesheets.