Add 'maybeToMonoid'?

[chshersh]

I propose to add next function:

maybeToMonoid :: Monoid m => Maybe m -> m
maybeToMonoid = maybe mempty id

When there was Foldable for Maybe, maybeToMonoid is just fold. But I think that this function is useful. And it's behavior and type is clear from name, also what it does and how also clear from type.

[gromakovsky]

Btw, maybe a id is fromMaybe a.

[chshersh]

@gromakovsky Even better :)

[chshersh]

One more convenient function is maybeWithMonoid :: Monoid m => Maybe a -> (a -> m) -> m. After it maybeToMonoid x becomes just maybeWithMonoid x id.