proposal: manage numbers with defined size and return an error if the value is out of range

[sbiemont]

The current behavior does not correctly handle numbers with a fixed size (such as uint8 or int16)

Unmarshal should return an error in the same way it does for float32 and float64, which are correctly managed

Example of a case where a "value out of range" is not detected:

type whatever struct {
	Value uint8 `env:"VALUE_UINT8,required"` // Value in [0; 255]
}

os.Setenv("VALUE_UINT8", "300")

var w whatever
_, err := env.UnmarshalFromEnviron(&w)
if err != nil {
	panic(err)
}
fmt.Println("w:", w)
// Prints 300 mod 256 = 44
// w: {44}