Tutorial for doing `wrapKey/unwrapKey` using `exportRawKey/encryptBytes` + `decryptBytes/importRawKey`

[jonasfj]

It would be nice to show using a tutorial (and tests) that we don't need to support wrapKey/unwrapKey because the functionality can be replicated using exportRawKey/encryptBytes and decryptBytes/importRawKey.

TODO:

• Test this for multiple key types.
• Explore if there is something unique about AES-KW, or if this can also be implemented using primitives we already have.
• Write tests that shows this works and produces the same result as it would in the browser.
• Write a doc/wrap-key.md tutorial demonstrating how to do this.