allow dashes and underscores, fixed incorrect command in guide

README.md

@@ -14,7 +14,7 @@ Either install GNOME or Minimal depending on if you intend to setup a server or
 Clone the repository to your home directory, you can do this by opening a shell with git installed.
 
 ```bash
-nixos-shell -p git
+nix-shell -p git
 git clone https://git.mvl.sh/vleeuwenmenno/dotfiles.git ~/dotfiles
 exit
 ```

setup.sh

@@ -45,7 +45,7 @@ prepare_hostname() {
     read hostname
 
     # Validate hostname to ensure it's not empty, contains only alphanumeric characters, and is less than 64 characters
-    while [[ -z $hostname || ! $hostname =~ ^[a-zA-Z0-9]+$ || ${#hostname} -gt 64 ]]; do
+    while [[ -z $hostname || ! $hostname =~ ^[a-zA-Z0-9_-]+$ || ${#hostname} -gt 64 ]]; do
         echo "Invalid hostname. Please enter a valid hostname:"
         read hostname
     done