fix: ViewCube example uses incorrect click event #76

[ynnob]

Description

Additional context

This PR fixes #76

• the ViewCube addEventListener was changed from "back" to "leftclick" to match the actual existing event and the doc description of this code block.
• an empty code block was removed (result of a duplicate description)

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following:

• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Follow the Conventional Commits v1.0.0 standard for PR naming (e.g. feat(examples): add hello-world example).
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.