message: Add comment regarding singleton pattern
diff: @@ -145,6 +145,10 @@ _configuration_ information for a contract. For example, in the
  there is a `Bucket` to look up name to name data, but we also have a `Singleton`
  to store global configuration - namely the price of buying a name.
  +Please note that in this context, the term "singleton" does not refer to
  +[the singleton pattern](https://en.wikipedia.org/wiki/Singleton_pattern) but a
  +container for a single element.
  +
  ```rust
  use cosmwasm_std::{Coin, coin};
  use cosmwasm_std::testing::MockStorage;
  