Added .ipynb files for option strategies / Fixed broken links in READ…

[idsts2670]

Overview
New Additions:

• Added new Jupyter notebooks (.ipynb) for option strategies (iron butterfly and bull put spread).

Updates to Existing Notebooks:

• Made minor modifications to existing notebooks (specifically, code cleanup and adding comments).

File Deletion:

• Deleted options-delta-hedging.ipynb
• Removed because it requires re-evaluation for improved reusability and to avoid unnecessary confusion.

README Modification:

• Fixed broken links to the .ipynb files in README.md.

Background
These changes were made to support new option strategies while also improving existing notebooks and improve concise documentation.

Testing
The newly added and updated notebooks have been executed locally to confirm they run correctly.