[config] Feature Request: Add support for `double` among built-in Option Types

[indraneel12]

It's very nice to have such built-in support for customized Option Types: https://pub.dev/packages/config#supported-option-types

Inconvenience

Although it contains support for numbers in integer format (via IntOption), there's currently no built-in support for double values. It's not impossible to achieve this functionality as a consumer of this package, because it can be done via extending its base class, but doing so for such a basic requirement feels a bit inconvenient and adds noise to the downstream codebase.

Suggestion

Please consider adding support for double values as well. I understand DoubleOption sounds weird, but there's another way via metaprogramming. I shall attach a PR herewith for your ready reference.