docs: enhance documentation for Builder and error handling functions

[m-mizutani]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @m-mizutani, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the documentation and provides practical examples for key functionalities within the goerr library. The changes aim to improve developer understanding and adoption of features like the Builder pattern for shared error context, the ID function for robust error comparison, and type-safe keys for attaching structured data to errors. By clarifying existing godocs and adding illustrative examples, the PR makes the error handling mechanisms more intuitive and easier to use.

Highlights

• Enhanced Documentation for NewBuilder: The godoc for NewBuilder has been expanded to clearly explain its utility in creating multiple errors that share a common context, such as a request ID or service name, without repetitive option specification.
• Clarified ID and With Function Documentation: The documentation for the ID function now better explains how it enables errors.Is() to compare errors by their ID string, facilitating sentinel-like error matching. The With function's godoc has also been improved to detail its use case for enriching errors in middleware and how it handles both *goerr.Error and standard errors.
• Updated Deprecation Message for WithTags: The Deprecated comment for the WithTags method has been updated to explicitly guide users to use the goerr.Tag option with goerr.New() or goerr.Wrap() as the preferred alternative.
• New Example for NewBuilder: An ExampleNewBuilder function has been added to builder_test.go, demonstrating how to effectively use the builder pattern to attach common contextual values to multiple errors.
• New Example for ID Function: An ExampleID function has been added to error_test.go, illustrating how to define an error with an ID and subsequently use errors.Is() for robust error type checking.
• New Example for NewTypedKey: An ExampleNewTypedKey function has been added to typed_values_test.go, showcasing the definition and usage of type-safe keys (UserIDKey, RequestIDKey) with goerr.TV() and goerr.GetTypedValue() for compile-time safety.

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[gemini-code-assist]

Code Review

This pull request provides excellent enhancements to the documentation and examples for the library. The updated comments for NewBuilder, ID, With, WithTags, and NewTypedKey are much clearer and more descriptive. The addition of Example functions for NewBuilder, ID, and NewTypedKey is a great way to provide runnable documentation and demonstrate the library's features effectively. All changes are well-implemented and improve the overall quality and usability of the project.