[FEAT] Update the monitoring demo to use the new Style API

[tbouffard]

Is your feature request related to a problem? Please describe.
The monitoring demo style edges by adding CSS classes. When the zoom level change, the stroke width doesn't follow the zoom level.
So, the stroke width may appear too large or too small depending on the zoom level.
This is the same for the arrow size.

Frequency use case paths not clearly

zoom level 1	zoom level 2

Time use case paths not clearly

zoom level 1	zoom level 2

Describe the solution you'd like
process-analytics/bpmn-visualization-js#1030 will provide a new way to style the BPMN Elements. Comparing to the CSS way, using the API set the value in the SVG DOM elements. So, the size of the stroke won't depend on the zoom level and then, the relative

Describe alternatives you've considered
Keep CSS classnames and still have the limitation.

Additional context
Once implemented, the image of the Process Analytics website should be updated as it displays a screenshot of this demo. Do something similar to process-analytics/process-analytics.dev#899.

Tasks

• implement the usage of the API feat: use the "Update Style" API in the monitoring demo #486
• update the website. Tracked in [FEAT] Update the screenshot of the "monitoring" use case process-analytics.dev#993