Fix - Custom Data key naming

[ItsNature]

Overview

Description:
Renames the item custom data keys documented for the inventory module from camelCase to snake_case, matching Minecraft's resource location conventions. The client accepts both spellings, so existing integrations keep working.

Changes:

• copyToClipboard -> copy_to_clipboard
• openUrl -> open_url
• suggestCommand -> suggest_command
• runCommand -> run_command
• hideItemTooltip -> hide_item_tooltip
• hideSlotHighlight -> hide_slot_highlight

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Review Request Checklist

• Your code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have tested this change myself. (If applicable)
• I have made corresponding changes to the documentation. (If applicable)
• The branch name follows the projects naming conventions. (e.g. feature/add-module & bugfix/fix-issue)

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