React-native-web: Upgrade Flow

[necolas]

Looking for help to upgrade Flow to the latest version.

We can @noflow most of the files and then migrate modules individually.

Also looking to start using Flow strict-local. You can look at the React Native codebase for examples of how to type components

[leggomuhgreggo]

@necolas I can lend a hand.

I figure the approach will be:

1. Upgrade flow-bin + bump the version in .flowconfig
2. Fix errors introduced by the new version
3. Incrementally add to flow interface definitions for the 70 or so untyped js files in packages/react-native-web, adding @noflow as needed
4. Incrementally add the strict-local flag, and fix errors

Some Questions:

1. Are there categories of modules you'd like to prioritize?
2. Any variation from the recommend @flow-strict patterns?
3. Did you want to continue using prop-types?
4. Any flow lint or eslint-plugin-flowtype rules you're interested to add?

Let me know how all that sounds 🤘

Thanks!

[necolas]

Thanks! Let's use the same version of flow as found in RN 0.57 release. Prioritise the exported modules. I'm not sure about prop types; they're being removed from RN but a lot of web people won't have flow setup

[necolas]

This is done in branch react-native-0.57