Add a --version|-v flag to display the project version

[davidbtadokoro]

Description:

Like most CLI apps, add a flag --version|-v to display the project version.

Motivation:

Although not utmost necessary, it is a great "quality of life" feature that doesn't seem complex to implement.

Idea:

Use the CARGO_PKG_VERSION environment variable from cargo. As it is exposed at compile time, it seems that the task is only displaying this value to the user.