fix(usePopper): fix exported Modifier type

[iz-podpolja]

As per title, fixes: #1012

[kyletsang]

Thanks for the PR. Could you run prettier on your code?

[iz-podpolja]

Thanks for the PR. Could you run prettier on your code?

Sure - done.

[kyletsang]

Thanks. Prettier looks good on the code, but we don't need those changes on the changelog

[kyletsang]

There's also this error

Type 'undefined' does not satisfy the constraint 'Obj'.

[iz-podpolja]

There's also this error

Type 'undefined' does not satisfy the constraint 'Obj'.

Ok, excluded the changelog.md from prettier output and added a util to proxify undefined with Popper.Obj.
Tests, lint & tsc --noEmit are green for me.

[kyletsang]

Thanks!