[10.0.0] Use of std.h fails without RTTI enabled

[dandee]

Trying to use "fmt/std.h" results in compilation error when RTTI is disabled.

/project/../../src/extlib/fmt/include/fmt/std.h:290:32: error: use of typeid requires -frtti
    const std::type_info& ti = typeid(ex);
                               ^

Reproduction:
https://godbolt.org/z/9fnbK3E5x

[vitaut]

We don't officially support building with RTTI disabled but a PR that makes that usage conditional would be welcome provided that it is not too intrusive. Alternatively, you can use {fmt} without fmt/std.h since the latter only provides some optional standard library formatters.