fix: adds missing export for InMemory accumulators

Author: lanterno

src/accumulator/index.ts

@@ -6,6 +6,7 @@ export * from './IAccumulatorState';
 export * from './IInitialElementsStore';
 export * from './kb-universal-accumulator';
 export * from './kb-acccumulator-witness';
+export * from './in-memory-persistence';
 export {
   VBWitnessUpdateInfo,
   KBUniversalMembershipWitnessUpdateInfo,