This commit adds a new file, "Mounting-Second-Disk.md", which provides instructions on how to mount a second disk to the system. The file includes step-by-step instructions on creating a mount point directory, formatting the disk (optional), mounting the disk, and configuring it to mount automatically on boot.

Additionally, the commit updates the README.md file to include a link to the new "Mounting-Second-Disk.md" file in the installation guide.

Lastly, the mkdocs.yml file is modified to add "Mounting second disk" to the navigation menu.

These changes aim to improve the documentation and provide users with clear instructions on how to utilize a second disk as a storage device.