Files and Serialization in Ruby: Add read and write videos to additional resources

[ssimkani]

Because

This change provides additional resources related to File I/O in Ruby. It includes two videos for reading and writing files by Giraffe Academy.

This PR

• Adds two videos for reading and writing files under 'Additional Resources'.

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum contributing guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
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• If any lesson files are included in this PR, they follow the Layout Style Guide