fix: correct boolean types

[samtjo]

Fixes: https://github.com/bvaughn/react-virtualized-auto-sizer/issues/70

Correcting the boolean types, as true and false aren't valid TypeScript types

[bvaughn]

as true and false aren't valid TypeScript types

This is incorrect. Boolean is a type that includes either true or false. true or false as a hard-coded value is just a constraint (same as you can provide a fixed string or number etc).

The reason this type has the permutations is that:

1. It makes no sense for both width and height to be disabled (so true+true would be an invalid combination)
2. To better match up the params passed to the onResize callback