Add styled text and table examples to jsPDF README (Hacktoberfest Contribution)

[KARLE-ATHARVA]

📄 Hacktoberfest Documentation Contribution

This PR adds two practical examples to the jsPDF README:

1. Styled Text Example – demonstrates how to use bold fonts and custom colors in PDFs.
2. Table Example – demonstrates creating a simple table using the jsPDF AutoTable plugin.

✅ Why this is helpful

• Many developers search for “how to style text” or “how to create tables in PDFs”.
• Examples are non-breaking, beginner-friendly, and ready to copy-paste into projects.
• Improves the README completeness and onboarding experience for new users of jsPDF.
• Keeps examples clearly separated and easy to understand.

Looking forward to feedback from maintainers! 🙌