Introduce generic UnionTypeAnnotation (facebook#54587)

Summary:

Adding the generic type T UnionTypeAnnotation. This will be used later to create Unions of types String, Number & Boolean.

Changelog: [Internal]

Differential Revision: D87374445

Author: arushikesarwani94

packages/react-native-codegen/src/CodegenSchema.d.ts

@@ -53,6 +53,11 @@ export interface ObjectTypeAnnotation<T> {
   readonly baseTypes?: readonly string[] | undefined;
 }
 
+export interface UnionTypeAnnotation<T> {
+  readonly type: 'UnionTypeAnnotation';
+  readonly types: readonly T[];
+}
+
 export interface MixedTypeAnnotation {
   readonly type: 'MixedTypeAnnotation';
 }

packages/react-native-codegen/src/CodegenSchema.js

@@ -72,6 +72,11 @@ export type ObjectTypeAnnotation<+T> = $ReadOnly<{
   baseTypes?: $ReadOnlyArray<string>,
 }>;
 
+export type UnionTypeAnnotation<+T> = $ReadOnly<{
+  type: 'UnionTypeAnnotation',
+  types: $ReadOnlyArray<T>,
+}>;
+
 export type MixedTypeAnnotation = $ReadOnly<{
   type: 'MixedTypeAnnotation',
 }>;