[FEAT] Implement the first iteration of the "Predictions demo"

[tbouffard]

This issue is tracking all issues of the first iteration. Only use the low-level APIs for now.
BPMN Diagram: Pizza diagram from the examples provided by the BPMN specification.

We will provide 2 use cases

• predicted late: vendor “Bake the pizza” in progress (started for 45 min for instance). Customer: predicted next task will be “Ask for pizza” after the complex gateway
• predicted on time: vendor “Deliver pizza” in progress. Customer, predicted "received pizza" (we will highlight the whole path/branch)
• Design: we use the same design as for the monitoring demo for legends, panels and tabs

We will work on the master branch. The demo will be publicly available in the live environment when the first iteration is completed.

Tasks

Beta Give feedback

1. [FEAT] 'Predictions Demo': initialize and display the Pizza diagram #261
   +0
   
2. Improve the Pizza diagram for a better rendering.
3. 1st attempt in #264
4. 2nd attempt in #266
5. [FEAT] 'Predictions Demo': style already executed paths #263
   enhancement +1
6. Highlight running elements #265
7. Highlight next predicted elements #275
8. On predicted paths highlight: make non predicted path less visible #522
9. Restore message flow icons in the BPMN diagram once #524
10. bug in bpmn-visualization is fixed: process-analytics/bpmn-visualization-js#1622
11. being able to style message flow icon precisely: process-analytics/bpmn-visualization-js#928
12. Review CSS to use rem instead of em or px (may be use in the 'pulse' animation) #523
13. Add legends #525
14. Display the demo in the HTML home page for a public access #529
15. Replace the duplicated PathResolver, of Bonita day demo, by the new plugin / expertimental extension. See #515 (comment). -> We don't use it anymore.
16. deactive the navigation #527
17. reference the demo in the main README #529
18. Update the description in the HTML page #529
19. review the README of the demo #529