Added Java Date and Time Solution and Updated Readme

[Pargat-Dhanjal]

Issue Number: #51

This submission will close the issue #

Submissions Checklist:

• Have you followed the guidelines in CONTRIBUTING.md?
• Have you checked there aren't other open Pull Requests for the same hackerrank problem?
• Have you successfully submitted your code in hackerrank?
• Is your file name exactly same as the problem name of hackerrank, followed by the proper extension?
• Have you ensured that you have put the files in appropriate folders? (Folders are made according to the subdomain of hackerrank practice problems).

Hacktoberfest Contributor:

• Are you a hacktoberfest contributor?

Hackerrank Problem Link: https://www.hackerrank.com/challenges/java-date-and-time/problem?isFullScreen=true

Submitted Hackerrank Solution Link: https://www.hackerrank.com/challenges/java-date-and-time/submissions/code/293511982

Any other changes you made or something you would like to mention?

Updated Readme File

[Riddhi9570]

Great! Thanks for contributing!