update path, comment format, add java, firebase

install/13-nvm.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+# nvm is installed
+if not_installed "nvm"; then
+
+    printf "Installing nvm...\n"
+
+    # Install nvm
+    run "https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.2/install.sh" \
+        "bash"
+    source "$NVM_DIR/nvm.sh"
+
+fi
+
+printf "nvm is installed, upgrading...\n"
+git --git-dir="$NVM_DIR/.git" pull
+nvm --version
+node --version
+npm --version