Parse .js.flow files with hermes-parser (#38726)

Summary:
Pull Request resolved: #38726

Changelog: [Internal]

Needed to fix spurious parser errors

Reviewed By: pieterv

Differential Revision: D47959263

fbshipit-source-id: 95ce244de41c5b4b53fd56c542d660944b7e216f

.eslintrc.js

@@ -24,7 +24,7 @@ module.exports = {
     // overriding the JS config from @react-native/eslint-config to ensure
     // that we use hermes-eslint for all js files
     {
-      files: ['*.js'],
+      files: ['*.js', '.js.flow'],
       parser: 'hermes-eslint',
       rules: {
         // These rules are not required with hermes-eslint