Stricter type for fromNullable

[Lior-Kiperman]

I'd like to strict the type of fromNullable of Option to allow only nullable values.

Something like this:

export const fromNullable: <A extends null | undefined>(a: A) => O.Option<NonNullable>

This allows us to:

1. Avoid unnecessary checks for values that cannot be nulls
2. Fix wrong types that are not nullable but should be (because actual values are nullable)

We use the eslint rule for "@typescript-eslint/no-unnecessary-condition", which helps us avoid useless checks for nulls and undefined and such. But when we use O.fromNullable it does not recognize it as an unnecessary condition.

I thought about overriding the type of fromNullable with - declare module 'fp-ts/Option'
Or adding a util function that simply calls O.fromNullable
Your thoughts and suggestions?