mio does not accept C++17 std::filesystem::path's for opening mapped files

[BullyWiiPlaza]

A small improvement suggestion I have is that mio does not accept an object of type std::filesystem::path for mapped file paths:

const std::filesystem::path file_path = "...";
mio::mmap_source mapped_file(file_path); // Will not compile

The filesystem library was added since C++17. Of course, you could just write the following right now and be all set:

const std::filesystem::path file_path = "...";
mio::mmap_source mapped_file(file_path.string());

But proper std::filesystem::path argument support would be nicer overall. The README says that this is a C++11 library but moving forward and upgrading it to a C++17 library wouldn't hurt, would it?

[DanielHerchenbach]

I agree. If I am not mistaken, under Windows this would also drastically simplify support of unicode characters in the file path. Under C++17, a path can be created from an utf8-encoded string by using std::filesystem::path myPath = std::filesystem::u8path(u8"äßçdé.txt"). All that is needed then is one single line: CreateFileW(myPath.wstring().c_str(), ... // use unicode version of fct'CreateFileW' and pass a wide character string