An extension to add inspect method to Option and Result types.
This allows doing something with the value contained in a Some, an Ok (with inspect) or an Err (with inspect_err) while passing the value on,
which can be useful for introducing side effects in debugging, logging, etc.
```rust use respector::prelude::*;
let some = Some(10);
assert_eq!(some.inspect(|x| println!("Some({})", x)), some); // Prints Some(10).
let ok = Ok::<_, ()>(10);
assert_eq!(ok.inspect(|x| println!("Ok({})", x)), ok); // Prints Ok(10).
let err = Err::<(), >(10);
asserteq!(Err(10).inspect_err(|x| println!("Err({})", x)), err); // Prints Err(10).
```