fix: replace broken file:// link with the public GitHub URL of the ca…

[CHRISLeGURU]

Description

Replace broken file:// demo link in Session 15 resources with the demo app GitHub URL.

Related Issue

Related to #267

Type of Change

Check the type of change this PR introduces:

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor (improves code structure or readability without changing functionality)
• Other (please describe):

Changes Made

• Fixed broken file:// link in Session 15 resources
• Replaced local file:///Users/tyty/Desktop/Demos/cardano-dapp-demo with the cardano-dapp-demo GitHub URL made by tyty: https://github.com/Emmanuel-Tyty/Demos/tree/main/cardano-dapp-demo

Checklist

Ensure you have completed the following steps before submitting your PR:

• My code follows the project's coding style and guidelines.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation (if applicable).
• My changes generate no new warnings or errors.
• I have added tests that prove my fix is effective or that my feature works.
• I have checked for merge conflicts.
• I have rebased my branch onto the latest main or master branch.