writelnQ method
Encloses obj with delimiter, adds a newline
symbol and adds the resulting String to the buffer.
Usage:
final b = StringBuffer();
b.writeQ(1);
b.toString() == '\'1\'\n'
Implementation
void writelnQ(
Object object, {
QuotationMark delimiter = QuotationMark.single,
}) {
write(delimiter.symbol);
write(object);
write(delimiter.symbol);
write('\n');
}