Fakestrate - Mock Substrate and IPFS storages so we can use @subsocial/api in Storybook

[siman]

We need to mock classes in this package:
https://github.com/dappforce/dappforce-subsocial-js/tree/master/packages/api/src

As a bonus: React context with reducers can be used to be able to update the state. But this could be not trivial, such as we need to mock the logic of the corresponding methods of Subsocial blockchain: createBlog(), createPost(), createComment(), etc.