Fixed TYPO in Placeholders README Section

[beanbeanjuice]

Pull Request

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Description

There were multiple typos in the placeholders section of the README. They are now fixed. Additionally, some items were moved around to better represent the actual placeholders.

Fixes #194

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Type of Change

• Bug Fix (Small Non-Code Breaking Issue)
• Bug Fix (Critical Code Breaking Issue)
• Feature (Something New Added to the Code)
• Improvement (Improving An Existing Section of Code)
• Documentation Update
• Security Vulnerability

Changes

• Internal Code
• Documentation
• Other: _____

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Test Configuration

• Hardware:
  • CPU: AMD Ryzen 7 5800x3D
  • GPU: Nvidia RTX 3080
  • RAM: 32 GB DDR4
• JDK: Java OpenJDK 17

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Checklist

• This pull request has been linked to the appropriate issue on GitHub. (Use the development section on the right.)
• 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.
• No warnings are produced when the code is run.
• Appropriate tests exist for this pull request.
• New and existing Maven CI tests have passed.
• The pull request is properly merging into the correct branch.
• All existing local code has been pushed to the GitHub repository.
• Changes have been documented in the current draft SimpleProxyChat Releases update.