Simplify Quickstart and Related Documentation for Better Developer Experience

[mintlify]

Original Instruction: Can you shorten my Quickstart page? I sell to developers and I think it isn't clear enough or at a grade 10 reading level.

This PR simplifies and enhances the documentation readability across multiple sections, with a focus on the Quickstart page. The changes aim to improve clarity and maintain a consistent grade 10 reading level, making the content more accessible to developers.

Key Changes:

• Simplified and shortened the Quickstart page for better initial developer experience
• Adjusted related documentation sections to maintain consistency
• Improved readability across authentication, integration, and API setup pages
• Streamlined technical explanations while preserving essential information

Modified Files:

• Primary focus: quickstart.mdx
• Related changes to authentication setup documentation
• Updates to integration guides
• Adjustments to API playground and configuration files

These changes maintain technical accuracy while presenting information in a more concise and accessible format, improving the overall developer experience.