chore(readme): update bootloader instructions

README.md

@@ -97,10 +97,12 @@ cd /mnt
 sudo nixos-install
 ```
 
-## how to deploy the config
+## how to deploy the inital config
+
+- Don't forget to install the bootloader, if you changed it since `nixos-install`
 
 ```bash
-$ sudo nixos-rebuild switch --flake .#host_name
+$ sudo nixos-rebuild --install-bootloader switch --flake .#host_name
 ```
 
 ## how to upgrade the system