Add Markdown Support

[Amir-Helali]

Changes:

• Updated the README file to reflect the added Markdown feature. Added an example of Markdown transformation. Updated the Display the help message section.
• Updated the contents of example3.md for testing.
• Added extra conditions to check for .md files in the code.
• Updated the error messages to reflect if no .md files were found.
• Updated the WriteHtml function to check for # character in order to convert it to HTML <h1>. If a markdown file has a heading1 in it, the text for heading1 will be used instead of the title.
• Updated the success message when a .md file is converted to HTML.
• Tested and made sure these additions didn't break the original code.

This fixes #14