Add 14 Great Learning courses

[Tashuuuu]

Fixes #29

By submitting this pull request I confirm I've read and complied with the below requirements 🖖

Requirements for your pull request

• The certificate/course you want to add has to be provided for free and not a trial membership or time-based offer.
• This pull request should have the name of courses/certificates in the format Add Name of Course(s)/Certificate(s).
  • ✅ Add Java Introduction
  • ❌ Update readme.md
• Your entry should be added at the bottom of the appropriate category.
• Not a duplicate. Please search for existing submissions.
• Make sure the course link is working.
• Has consistent formatting and proper spelling/grammar.
  • Consistent and correct naming. For example, Node.js, not NodeJS or node.js.
• To verify that you've read all the guidelines, please comment on your pull request with just the word unicorn.

[waleedsadek-panx]

Looks good! Accepted and merged!

[waleedsadek-panx]

Thanks for your contribution! 🎉