Added Many type

Author: Ben Grynhaus

libs/core/src/lib/declarations/many.d.ts

@@ -0,0 +1 @@
+export type Many<T> = T | T[];

libs/core/src/lib/declarations/public-api.d.ts

@@ -3,5 +3,6 @@
 
 export * from './index-signature';
 export * from './known-keys';
+export * from './many';
 export * from './omit';
 export * from './string-map';