Add "recursive" option to `FileSystem.watch`

[jclem]

What is the problem this feature would solve?

This would make it easier to recursively watch changes in a directory with the Node platform, rather than only changes at the top level of the watched directory.

What is the feature you are proposing to solve the problem?

Adding the recursive option to the FileSystem API. See the Node.js documentation for information about this option.

What alternatives have you considered?

Wrapping the Node.js-native fs.watch API manually—effectively just copying the Effect implementation and adding support for the option.