fix: add phantom export to prevent empty types.ts compilation error (#6221)

Author: rajk93

packages/typegen/src/templates/tsDef/types.hbs

@@ -3,3 +3,5 @@
 {{#each items}}
 export * from './{{{this}}}/types.js';
 {{/each}}
+
+export type PHANTOM_GENERATED = 'generated';

packages/types/src/interfaces/types.ts

@@ -78,3 +78,5 @@ export * from './vesting/types.js';
 export * from './xcm/types.js';
 export * from './xcmPaymentApi/types.js';
 export * from './xcmRuntimeApi/types.js';
+
+export type PHANTOM_GENERATED = 'generated';