bug: defaultStepFunctionProps.conversionOptions must be present or Lambda invoke is not added to role

[dmeehan1968]

Lambda invoke permissions should be being added to any created lambda's (according to #52).

However, this doesn't happen unless conversionOptions is specified as part of defaultStepFunctionProps (not to be confused with the same property on the TypescriptStateMachineProps).

This must be fully specified, and the type only allows true for the three properties.

This is the case regardless of whether a role is supplied to the defaultStepFunctionProps or not.

new ts2asl.TypescriptStateMachine(this, "TypescriptStateMachine", {
  programName: "hello-world",
  defaultFunctionProps: {},
  defaultStepFunctionProps: {
    stateMachineType: "EXPRESS",
    role: executionRole,
    conversionOptions: {
       emitIamPolicies: true,
       emitStateLanguageFiles: true,
       autoGenerateIamPolicy: true,
   },
  },
  sourceFile: "./src/program.ts",
});