Add proper formatting strings for text output.

[p-costa]

• If double precision: (*(es24.16e3,1x))

• If single precision: (*(es15.8e2,1x))

  See: https://github.com/fortran-lang/stdlib/blob/57cfaf011ee11001b35bbdde43841a5a1f8cf443/src/stdlib_io.fypp#L23-L32