In https://github.com/status-im/status-desktop/commit/a90a30af1 we've introduced the functionality to import
communities through the UI via a community private key.
That private key is being validated before it gets imported.
For some reason, validation has been removed in another refactor
later on in https://github.com/status-im/status-desktop/commit/534cb23e1, rendering the import
functionality broken.
This commit re-introduces the `validate()` method to make importing
communities work again.