Update character name/health display documentation

[blueflamems]

Added player movement speed and run speed details to the character name/health display documentation.

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[github-actions]

The content quality library markdownlint says:

• First line in a file should be a top-level heading (MD041/first-line-heading/first-line-h1)

For more information, see the Markdownlint docs for MD041/first-line-heading/first-line-h1.

⛔️ This change is a requirement. Please fix it before merging.

[github-actions]

Hi @blueflamems, thanks so much for helping improve the Roblox creator documentation! Our technical writing team will review your pull request soon. In the meantime, please ensure you've read through the README.md, contribution guidelines, and style recommendations.