updated linux.md cheatsheet

[ravi0900]

Change Summary

Added New useful commands

• cd -
• shutdown -p +M
• open .

Added new tools section

• ncdu
• neofetch
• htop

Checklist

Linux.md updated

General

• [x] This Pull Request is all my own work. (You'll be blacklisted if you are caught for plagiarism.)
• [x] I've read CONTRIBUTING.md
• [x] I've made some valid changes to the CheatSheet, and they are not just minor changes.

Changes

• [x] I've read and followed the Solution Template

[netlify[bot]]

❌ Deploy Preview for cheatsheets failed.

Name	Link
🔨 Latest commit	b2c30e819d7ea50085646ab60618712a5ce06143
🔍 Latest deploy log	https://app.netlify.com/sites/cheatsheets/deploys/652431b26d52a50008c23b5c

[ravi0900]

@aryankashyap7, please merge this, and help what failed here, in local environment is was working fine.