Did you extract all the files in the .zip? libvorbisfile.so.3 should be in the game directory. Also, make sure you run the .sh file, not the executable, as it sets the path to find those libraries.
On the itch.io page, it should have the following instructions right?
Linux: Extract the .zip file and run Aground.sh (you may need to set it's permissions to be executable). If you're running a 64-bit version of Linux, you may also need to install the following libraries: libglu1-mesa:i386, libpulse0:i386.