✨ Add callback function for middleware/logger

[panjf2000]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.
Explain the details for making this change. What existing problem does the pull request solve?

Fixes #2218

Type of change

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• New feature (non-breaking change which adds functionality)

Checklist:

• For new functionalities I follow the inspiration of the express js framework and built them similar in usage
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation - Update docs of logger docs#302 for https://docs.gofiber.io/
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• If new dependencies exist, I have checked that they are really necessary and agreed with the maintainers/community (we want to have as few dependencies as possible)
• I tried to make my code as fast as possible with as few allocations as possible
• For new code I have written benchmarks so that they can be analyzed and improved

Commit formatting:

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