[Proposal] Add Cognitive Complexity as new option

Introduction

I would like to request to add "Cognitive Complexity" to this library as an option to select in the CLI and through hooks. This is a common quality check in the SonarQube application, used by many for static code checking.

Please see this document written by Sonar: https://www.sonarsource.com/docs/CognitiveComplexity.pdf. Importantly: "Unlike Cyclomatic Complexity, Cognitive Complexity adds a fundamental increment for each method in a recursion cycle, whether direct or indirect".

I am curious as to the opinions of others :)

Example 1

I like the example in the PDF, where the Cyclomatic Complexity is the same, but the Cognitive Complexity is vastly different:

Example 2

Consider the following code:

for _ in [i for i in range(5)]:
    for _ in [i for i in range(5)]:
        for _ in [i for i in range(5)]:
            for j in [i for i in range(5)]:
                if j == 2:
                    ...
                else:
                    if j > 3:
                        ...

The Cyclomatic Complexity, also the one currently reported bymccabe, is 7:

The Cognitive Complexity, as reported by Sonar, is 22 due to all of the nesting.

Start by reviewing the requested Cognitive Complexity definition in the linked Sonar document, then inspect the CLI and hooks entry points mentioned in the issue. Define how the metric should handle nesting and recursion, and verify that it can be selected and reported through both interfaces.