Update setup.sh to run from anywhere

Git submodule cloning was the last action that needed the script to be
run from within the dotfiles folder. Now, that part runs in its own
subshell that changes to the dotfiles folder context, allowing setup.sh
to be run from anywhere e.g. `~/dotfiles/setup.sh` instead of only
`./setup.sh`

setup.sh

@@ -51,8 +51,7 @@ git config --global diff.mnemonicPrefix true
 echo "Git config done."
 
 # Initialise and clone any submodules
-git submodule sync
-git submodule update --init
+(cd ~/dotfiles && git submodule sync && git submodule update --init)
 echo "Submodules done."
 
 # Zsh