Added install Node function

Necessary to ensure Node is installed using the latest stable release
by default.

lib/installers.sh

@@ -188,6 +188,15 @@ install_program() {
 }
 export -f install_program
 
+# Installs Node.
+# Parameters: None.
+install_node() {
+  if ! command -v fnm > /dev/null; then
+    $(get_homebrew_bin_root)/fnm install --lts
+  fi
+}
+export -f install_node
+
 # Installs Ruby.
 # Parameters: None.
 install_ruby() {