feat: add cacheFactory option to createMockClient for custom cache support

[Copilot]

Summary

The @graphitation/apollo-mock-client package hardcodes InMemoryCache in createMockClient, preventing use of custom Apollo cache implementations like ForestRun. This PR adds a cacheFactory option so users can provide their own cache.

Changes

src/index.ts

• Added cacheFactory option to createMockClient options:

  cacheFactory?: (possibleTypes: Record<string, string[]>) => ApolloCache<NormalizedCacheObject>

• When cacheFactory is provided, it receives the computed possibleTypes (derived from the schema) and returns a custom cache instance
• When cacheFactory is not provided, the default InMemoryCache behavior is preserved (fully backward compatible)

Tests

• 3 unit tests for the generic cacheFactory option (default behavior, custom factory usage, possibleTypes passing)
• 2 integration tests with ForestRun cache (instantiation and full query resolution with component rendering)

Usage

import { ForestRun } from "@graphitation/apollo-forest-run";
import { createMockClient } from "@graphitation/apollo-mock-client";

const client = createMockClient(schema, {
  cacheFactory: (possibleTypes) => new ForestRun({ possibleTypes }),
});