Add warning when deleting account that you cannot create a new account with the same username later

[cipherself]

So, I created an account to try the client then decided to delete it only to discover later on that I can't create a new account with the same username :(, I suggest that a warning be added during the confirmation step of the deletion step signifying this and linking to https://stellarorg.zendesk.com/hc/en-us/articles/203344699-I-deleted-my-account-but-now-I-can-t-open-an-account-with-my-old-username