adding warning about sketchy commands

Author: matyikriszta

command-line/introduction/tutorial.md

@@ -11,6 +11,8 @@ The command line is a text interface for your computer. Just like Windows Explor
 
 To access the command line, we use a terminal emulator, usually called a terminal. On Mac OSX you can access the terminal by opening the Terminal application from your Applications folder. On Windows you should use a program called the PowerShell. To access the Powershell, click 'Start', in 'Search programs and files' type powershell, and hit enter. This should open up Powershell on your computer.
 
+Before we get started, you should note some DO's and DONT's while using the command line. The command line is a powerful tool that can significantly speed up your workflow but can also irreversibly harm your computer so make sure you use it responsibly. If you are not sure what a command does DO NOT type it into your terminal. The command `rm -rf /` is a classic one that you should never use. If you are stuck and in need of help make sure you ask from someone you trust or other reputable sources. It goes without saying that all commands in this tutorial are safe to use.
+
 ## Example 1: navigating around in the terminal
 
 Once you opened up your terminal, type in the following after the `$` or `>` sign and hit enter: (`$` or `>` is the prompt, you don't have to retype that in the terminal, only the characters that come after them):