Add demonstration how to mock transferred_balance (#555)

* [chores] implicitely ➜ implicitly

* [examples] Add demonstration of how to mock transferred_balance

* [lang] Fix clippy 'needless_lifetimes'

Error was:

explicit lifetimes given in parameter types where they could
be elided (or replaced with `'_` if needed by type declaration)

* [lang] Apply cargo fmt

* [examples] Fix param