Refactored Program.cs

- Introduce ResourceFiles.cs with constants for JSON resource paths.
- Updated Program.cs to use those constants.
- Refactored scene handling to store current scene in a variables.
- Added file existence checks and switch quit handling to sys.Environment.Exit.
- Updated .editorconfig.

.editorconfig

@@ -13,9 +13,6 @@ indent_style = space
 
 # C# files
 [*.cs]
-# Nullable reference types
-csharp_nullable_reference_types = enable
-
 # Naming conventions
 dotnet_naming_rule.async_methods_end_in_async.severity = suggestion
 dotnet_naming_rule.async_methods_end_in_async.symbols = async_methods
@@ -27,6 +24,16 @@ dotnet_naming_symbols.async_methods.required_modifiers = async
 dotnet_naming_style.end_in_async.required_suffix = Async
 dotnet_naming_style.end_in_async.capitalization = pascal_case
 
+# Constants are UPPERCASE
+dotnet_naming_rule.constants_should_be_upper_case.severity = suggestion
+dotnet_naming_rule.constants_should_be_upper_case.symbols = constants
+dotnet_naming_rule.constants_should_be_upper_case.style = constant_style
+
+dotnet_naming_symbols.constants.applicable_kinds = field, local
+dotnet_naming_symbols.constants.required_modifiers = const
+
+dotnet_naming_style.constant_style.capitalization = all_upper
+
 # Formatting
 csharp_new_line_before_open_brace = all
 csharp_indent_case_contents = true