This type is for our use of the Swipeable from react-native-gesture-handler, which uses the Animated library that is built into React Native. Separating this diff out so it's clear why I'm introducing the type.
NOTE: CI will fail on this diff. I considered the possibility of fixing Flow errors BEFORE upgrading Flow, but it wasn't possible... in some cases, the fixes to support the new version of Flow caused errors in the old version. I could have hidden these type errors with $FlowFixMe lines and then later revert those, but that seemed like too much busy work.
Depends on D10006