Updated Node package install script to use NPM

Yarn has fallen out of favor in the community so have switched to
native NPM support instead.

lib/utilities.sh

@@ -101,15 +101,15 @@ get_install_root() {
 }
 export -f get_install_root
 
-# Checks Yarn has been installed and exits if otherwise.
+# Checks NPM has been installed and exits if otherwise.
 # Parameters: None.
-check_yarn_install() {
-  if ! command -v yarn > /dev/null; then
-    printf "%s\n" "ERROR: Yarn can't be found. Please ensure Homebrew and Yarn have been installed."
+check_npm_install() {
+  if ! command -v npm > /dev/null; then
+    printf "%s\n" "ERROR: NPM can't be found. Please ensure Homebrew and NPM have been installed."
     exit 1
   fi
 }
-export -f check_yarn_install
+export -f check_npm_install
 
 # Checks Mac App Store (mas) CLI has been installed and exits if otherwise.
 # Parameters: None.

lib/verifiers.sh

@@ -129,13 +129,13 @@ export -f verify_path
 
 # Checks for missing Node packages.
 verify_node_packages() {
-  local packages=$(yarn global list --json | grep '"type":"info"')
-
   printf "\nChecking Node packages...\n"
 
   while read line; do
-    if [[ "$line" == "yarn global add"* ]]; then
+    if [[ "$line" == "npm "* ]]; then
       local package=$(printf "$line" | awk '{print $4}')
+      local packages=($(npm list --global --depth=0 | grep "$package"))
+
       verify_listed_application "$package" "${packages[*]}"
     fi
   done < "$MAC_OS_CONFIG_PATH/bin/install_node_packages"