Enhance Error Messaging, Fix README Typos, and Improve Markdown Formatting

[r3econ]

This PR addresses several improvements to the codebase:

• Enhanced Error Messaging: Updates the error description for expired Figma personal authentication tokens to include actionable troubleshooting guidance, improving user experience during debugging.
• README Fixes: Corrects typos in README files for better readability and professionalism.
• Markdown Improvements: Refines markdown formatting for consistency and clarity.

Background

Previously, when a Figma personal authentication token expired, the library returned a misleading error:
text:

Error: Figma file not found. Check lightFileId and darkFileId (if your project supports dark mode) in the yaml config file.

This error failed to indicate an expired token as a potential cause, complicating troubleshooting. This PR updates the error message to explicitly address the expired token scenario, making it easier for users to diagnose and resolve the issue.

Changes Made

• Modified error handling logic to include specific guidance for expired Figma authentication tokens.
• Fixed typographical errors in README files.
• Standardized and improved markdown formatting across documentation.

[subdan]

Thanks!