Added date-calc project

[clin8328]

Type of change

• Added new project
• Bug fix
• New features
• Enhanced documentation

Changes proposed in this pull request

• Project name :

Date-Duration-Calc

• Short description :

This project will allow the user to input two dates and the program will return the difference between the two dates.
This is for hacktoberfest

Checklist

• The code is Python 3 compatible
• I have added relevant comments in my file to make code understandable
• I have added my project in a folder which includes all the necessary files

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