add IsoDateString type as an alias

test/__snapshots__/lib.test.ts.snap

@@ -29,6 +29,8 @@ exports[`createRecordType handles file fields with multiple files 1`] = `
 exports[`generate generates correct output given db input 1`] = `
 "// This file was @generated using pocketbase-typegen
 
+export type IsoDateString = string
+
 export enum Collections {
 	Books = "books",
 }

test/lib.test.ts

@@ -159,7 +159,7 @@ describe("createTypeField", () => {
         name: "dateField",
         type: "date",
       })
-    ).toEqual("\tdateField: string\n")
+    ).toEqual("\tdateField: IsoDateString\n")
     expect(
       createTypeField({
         ...defaultFieldSchema,