Add source_location feature to print source filename and line number

[zao111222333]

When source_location feature is turn on and .with_source_location(true) is set, logger will print filename and line number.

And I also add the example, just run

cargo run --example source_location --features source_location

You will see

2025-05-30T16:48:04.974Z WARN  [simple_logger/examples/source_location.rs:6 source_location] This is an example message.

close #76