load abstract method
Load messages from the given resource.
This method should parse the resource content according to the loader's format and return a flat map where keys are message codes and values are message templates.
Parameters:
resource
: The resource to load messages from
Returns a Future that resolves to a map of message codes to templates.
Example:
final resource = AssetPathResource('messages.json');
final messages = await loader.load(resource);
print(messages['greeting']); // "Hello {0}!"
Implementation
Future<Map<String, String>> load(AssetPathResource resource);