Make it possible to include log record.file() / record.line()

[brandonros]

https://stackoverflow.com/questions/61810740/log-source-file-and-line-numbers I could be wrong but I think at the moment such functionality is impossible with this library?

[fvacek]

I also like to have this feature, it's hard to find origin of log message in source code, what makes bug hunting more difficult. My implementation is here. https://github.com/borntyping/rust-simple_logger/pull/86/commits/e0abd42227452a29a3a7029b89c99b7165c32131