Update README.md for Black

[rupalilakhanpal]

Updated the readme.md for the game black jack with instructions on how to play blackjack.

PR Description 📜

Please include summary related to the issue you have fixed and describe your PR in brief over here by specifying the issue number on which you were working below
Fixes # <your_issue_number>

---

Mark the task you have completed ✅

• I follow CONTRIBUTING GUIDELINE & CODE OF CONDUCT of this project.
• I have performed a self-review of my own code or work.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generates no new warnings.
• I have followed proper naming convention showed in CONTRIBUTING GUIDELINE
• I have added screenshot for website preview in assets/images
• I have added entries for my game in main README.md
• I have added README.md in my folder
• I have added working video of the game in README.md (optional)
• I have specified the respective issue number for which I have requested the new game.

---

Add your screenshots(Optional) 📸

---

Thank you soo much for contributing to our repository 💗

[kunjgit]

Thank you @rupalilakhanpal ,for creating the PR and contributing to our GameZone 💗
Review team will review the PR and will reach out to you soon! 😇
Make sure that you have marked all the tasks that you are done with ✅.
Thank you for your patience! 😀

[kunjgit]

Hey @rupalilakhanpal,
Please make sure to link the relevant issue using the appropriate syntax, such as "#issueNumber" 👀.
Follow the proper guideline and make a new PR again 😀.
Happy Hacking 💗

[kunjgit]

Thank you @rupalilakhanpal , for your valuable time and contribution in our GameZone 💗.
It’s our GameZone, so Let’s build this GameZone altogether !!🤝
Hoping to see you soon with another PR again 😇
Wishing you all the best for your journey into Open Source🚀