docs: mention the skip-changelog label

[Flash0ver]

Summary

Mention the skip-changelog GitHub label in regards to the auto-changelog generated by Craft.

Remarks

When reviewing #5178, an Agent mentioned:

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Remaining minor/low-severity items (not blocking)

1. Missing #skip-changelog — per this repo's convention (CLAUDE.md), non-user-facing changes should carry this tag. This PR touches only dev tooling/docs, never ships in the NuGet packages, and the title (Add optional pre-commit hook...) doesn't follow the type: description convention used elsewhere in this repo's changelog (chore:, docs:, etc.). Actionable: add #skip-changelog to the description, or retitle to chore: add optional pre-commit hook for code formatting.

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The Agent is currently oblivious to the skip-changelog GitHub label:

This change should be teaching the Agent to consider the Labels too.

#skip-changelog