stub out non-web dependencies

[FLGMwt]

Hopefully fixes #95

Took a guess at naming / file location, let me know if there's somewhere we'd rather have these.

I could use some help testing this out as I'm not sure I'm doing the right thing to test this out. Here's what I tried:

1. Create new expo project
2. Add navigation/ex dependencies necessary for the stack example (https://reactnavigation.org/docs/en/next/hello-react-navigation.html)
3. Make change in this branch to add stubs
4. yarn lerna run prepare to build (I think? pulled from circle config)
5. cd packages/stack && yarn link
6. cd /my-expo-project && yarn link @react-navigation/stack && yarn add @react-navigation/stack
7. ^ that somehow didn't pull in safe-area-view & @react-navigation/routers so I added them explicitly
8. TypeError: Cannot call a class as a function errors from @react-navigation/core/lib/createNavigator.js, so I think I'm on the wrong path. How do y'all normally test react-navigation locally?

Any help would be appreciated!

[FLGMwt]

I would have done platform.Select in a single "utils/MaskedViewStub.ts" file except that @react-native-community/masked-view makes a call to requireNativeComponent on module initialization so it blows up on web. The component noop should never be used, but I can make it least be a passthrough <View>{children}</View> if that's preferred.

[satya164]

Thanks @FLGMwt. I'll do some tweaks and merge it.

[FLGMwt]

For sure, go for it. Thanks much :)