Added Linux Cheat Sheet in README.md

[SHASHANK0712]

Added Linux Command Line Cheat Sheet

Contributing

If you want to add a project to this list, please make sure that:

• You read the contributing guide
• The repository has hacktoberfest as topic and counts for hacktoberfest event
• The project can't be just an "add your name" or simply + 1 contribution to hacktoberfest
• Place them in alphabetical order
• One repository per PR/contribution - avoid conflicts and simplify review
• Your pull request is not spammy just adding an empty line, otherwise it will be marked as invalid and not count to hacktoberfest.

If they meet the requirements above, feel free to create a PR. Happy Hacking! ✨

[SHASHANK0712]

Hello @OtacilioN, I request you to please accept this PR. It will count to my Hacktoberfest contribution.

[SHASHANK0712]

@OtacilioN Please review and merge it. I have resolved the conflicts also.