[FEAT] Update the Hacktoberfest demo to introduce the theme for year 2022

[tbouffard]

Is your feature request related to a problem? Please describe. Last year we introduce a way to display both the 2020 and 2021 themes: #241 and #242. Let's add a new theme to advertise the 2022 event.

Describe the solution you'd like Use the colors of the 2022 events as much as possible. To do that, open https://hacktoberfest.com, and use the inspection of the page code from your browser to get the colors of the page. This year, the brand guidelines are available at https://do.co/hacktoberbrand (in a Figma)

Tasks

• [x] update the preview image displayed in the HTML home page: #400
• [ ] If possible, improve the layout of the diagram: currently, we start left to right, and finish right to left which is not the usual way for the BPMN layout.
• [ ] Let pass query parameters to choose the year and the theme. This is useful for testing and bookmarking a dedicated theme variant
• [ ] Check if we can add a "halo" on the background of the pool for the dark theme
• Add interactions
  • [ ] Check that interaction are kept when changing the project name
  • [ ] Task including the Hacktoberfest url: make it clickable and redirect to the Hacktoberfest website in a new window/tab
  • [ ] Task about "Find an issue": make it clickable and redirect to the list of issues in a new window/tab. Warn this link may not work when not connected to github (add popover?) Consider an alternative url that doesn't require to be authenticated (https://github.com/issues?q=is%3Aissue+is%3Aopen+org%3Aprocess-analytics+archived%3Afalse+sort%3Aupdated-desc+label%3Ahacktoberfest isn't compliant to this
• Update the demo description
  • [ ] state that some elements are clickable
  • [ ] have less lines to reduce the need for scrolling. For instance: Interact with the diagram (find the clickable elements), Make it your own: change the project name to yours and share