feat: Allow merging multiple payloads for a single type

[atomrc]

This will allow merging payloads together and generates union types for those payloads

{
   First: [
      { type: "first", value: 1, first: 1 },
      { type: "first", value: 2 },
   ],
 }

Will generate

type First = {type: "first", value: number, first?: number}
                                          // ^ first has been automatically infered optional