feat: Re-Crypt an existing Storage instance (storage.encrypt(..))

[mrousavy]

const storage = new MMKV({ id: 'my.test.storage' })

storage.encrypt('my-private-key') // <-- encrypt with key 'my-private-key'
storage.set('test', 'works!')

storage.encrypt(undefined) // <-- remove encryption
storage.set('test', 'still works!')

closes: #179

[ddikodroid]

so to encrypt, i need to call storage.encrypt('key') or storage.recrypt('key')?

in the README.md it stated like this

// encrypt all data with a private key
storage.recrypt('hunter2')

// remove encryption
storage.recrypt(undefined)

[mrousavy]

recrypt, I renamed it - will release an update soon