[change] Add generated Flow files to package dist

Fix necolas#1684
Close necolas#1982

src/index.js

@@ -1,3 +1,4 @@
+// @flow strict
 export { default as unstable_createElement } from './exports/createElement';
 export { default as findNodeHandle } from './exports/findNodeHandle';
 export { default as processColor } from './exports/processColor';