IMPROVE - Empty `DashboardView`

[mikaelacaron]

Describe the feature you want to improve

• DashboardView has this text when the view is empty (meaning a user hasn't added their vehicle yet)
• Add a button below this text that says "AddVehicle" and show the AddVehicleView as a sheet

if viewModel.events.isEmpty {
Text("Add your first maintenance", comment: "Placeholder text for empty maintenance list prompting the user to add a maintenance event")
   // ...
}

[!NOTE] Leave the closure for AddVehicleView nil because this will be something that is going to be in a different PR (the actual functionality to add a vehicle is in the SettingsViewModel, and not accessible here), and I want that refactor in a different PR

Describe alternatives you've considered

• N/A

[ItsJakeMarcus]

This looks like a fun one :)