[standards][flow] Set up .flowconfig to support Haste and path-based imports

[ide]

Summary

See #24316 for the motivation.

By adding the .android.js and .ios.js extensions to the respective .flowconfig files, Flow is able to find files that either:

• Are required using Haste
• Are required using standard paths and have a .js extension
• Are required using standard paths and have a .platform.js subextension

Changelog

[General] [Changed] - Adjusted .flowconfig to support both Haste and standard path-based requires

Test Plan

After replacing some Haste-style requires with path-based requires, this change to the Flow config made Flow pass.

[cpojer]

Let's see what happens when I import that to FB, I may need to make some internal changes.

[facebook-github-bot]

@cpojer is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[ide]

I may need to make some internal changes.

Hopefully it is straightforward -- the concept here is that there were several files (namely those ending in .platform.js) that Flow was able to find only via Haste names. This commit teaches Flow about .platform.js, and when you specify module.file_ext, you override the defaults and need to re-specify all the extensions you use.

[react-native-bot]

This pull request was successfully merged by @ide in 682e11a.

^{When will my fix make it into a release? | Upcoming Releases}