Show error dialog when imported collection or environment is invalid

[alexandrehtrb]

Currently, when an invalid collection or environment file is imported and its contents are invalid, no error message appears. It would be good to have an indication to the user that the imported file is invalid.

The logic would need to be added in else clauses of the TryImport... calls:

Pororoca/src/Pororoca.Desktop/ExportImport/FileExporterImporter.cs

Lines 250 to 265 in 82889e7

	// First, tries to import as a Pororoca collection
	if (isPororocaCollection)
	{
	if (TryImportPororocaCollection(fileContent, preserveId: false, out var importedPororocaCollection))
	{
	mwvm.AddCollection(importedPororocaCollection!);
	}
	}
	// If not a valid Pororoca collection, then tries to import as a Postman collection
	else
	{
	if (TryImportPostmanCollection(fileContent, out var importedPostmanCollection))
	{
	mwvm.AddCollection(importedPostmanCollection!);
	}
	}