Allow chat events to be cancelled

[KabanFriends]

Pull Request

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Description

Adds a simple condition check in onPlayerChat so that SimpleProxyChat will not send chat messages if the chat event was cancelled. Despite Velocity API marking PlayerChatEvent's result as deprecated, chat cancelling will still work if you have plugins like SignedVelocity installed.

Closes N/A

Related PRs: N/A

Prerequisites: N/A

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Checklist

• The code follows the style guidelines.
• A self-review of the code was performed on GitHub.
• Appropriate comments and javadocs were added in your code.
• Appropriate changes have been made to the documentation.
• Appropriate changes have been made to the README.md file.
• Appropriate tests exist for this pull request.