docs: enhance non-assertive map access anti-pattern documentation

[abreujp]

• Add comparison table for access notations
• Improve explanations with clearer examples
• Add example of error propagation
• Include guidance for when to use each access method
• Format examples for better readability

[abreujp]

Thank you @sabiwara for your valuable feedback!

I've updated the pull request with all your suggested changes:

1. Added a "Map is nil" column to the table showing behavior when the map itself is nil
2. Added rows for Map.get(map, :key) (required map, optional key) and Map.fetch!(map, "key") (support for non-atom keys)
3. Combined the error propagation example with the bad_point example, with an adapted explanation
4. Added a summary section at the end of the explanation that recaps the different access methods, including pattern-matching

I'm new to open source contributions and still learning the best practices, so I truly appreciate your detailed review. Your guidance helps me improve both the documentation and my understanding of how to contribute effectively.

Let me know if you'd like any further adjustments!

[josevalim]

Thank you @abreujp! I have submitted some changes to remove the duplication and streamline it. If you are happy with it, let me know and I will merge it!

[abreujp]

Yes, I agree, thank you. @josevalim

[josevalim]

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