add 'linuxupskillchallenge'

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -857,6 +857,7 @@ performance of any of your sites from across the globe.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://www.tecmint.com/"><b>TecMint</b></a> - the ideal Linux blog for Sysadmins & Geeks.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://www.omnisecu.com/index.php"><b>Omnisecu</b></a> - free Networking, System Administration and Security tutorials.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/cirosantilli/linux-cheat"><b>linux-cheat</b></a> - Linux tutorials and cheatsheets. Minimal examples. Mostly user-land CLI utilities.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://github.com/snori74/linuxupskillchallenge"><b>linuxupskillchallenge</b></a> - learn the skills required to sysadmin.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="http://cb.vu/unixtoolbox.xhtml"><b>Unix Toolbox</b></a> - collection of Unix/Linux/BSD commands and tasks which are useful for IT work or for advanced users.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://linux-kernel-labs.github.io/refs/heads/master/index.html"><b>Linux Kernel Teaching</b></a> - is a collection of lectures and labs Linux kernel topics.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://peteris.rocks/blog/htop/"><b>htop explained</b></a> - explanation of everything you can see in htop/top on Linux.<br>