Changelog for Demo Generator 0.9.0

Changes

• Generator universal_event was renamed to story_modeller
• update universal event message protocol (PR, #6299)
• universal_event: Add editing mode (PR, #6296)
• story_modeller: stories implementation (PR, #6289)
• story_modeller: Add version support to event and story updates (PR, #6344)
• Upgrade Elixir to 1.16 and OTP to 26 (PR, #6284)
• story_modeller: Add future incident severity to templates (PR, #6350)
• Rewrite authentication/authorization so that the token is stored in session (PR, #6350)
• story_modeller: add story actors synchronization (PR, #6290)
• story_modeller: Add actions to trigger asset type refresh (PR, #6384)
• Update Phoenix, LiveView and other dependencies (PR, #6281)