[FEAT] Allow to select theme, year and project name when loading the Hacktoberfest demo

[tbouffard]

Is your feature request related to a problem? Please describe.
Consider some query parameters to change the state of the page at load time. This is useful for testing, bookmarking or taking screenshot of a dedicated theme variant.

Describe the solution you'd like
List of available parameters

• choose the year
• choose the theme.
• update the project name

Additional context
Be aware of:

• check what has been done for the monitoring demo: feat(monitoring-demo): select use case with query parameter #457
• see this proposal to generalize the parameters processing: https://github.com/process-analytics/bpmn-visualization-examples/pull/457/files#r1104569661