build: enable npm for php/python builds (#1133)

* build: enable npm for php/python builds

* update comment

.kokoro-autosynth/build-in-docker.sh

@@ -28,6 +28,23 @@ ssh-keyscan github.com >> "$HOME/.ssh/known_hosts"
 # Kokoro exposes this as a file, but the scripts expect just a plain variable.
 export GITHUB_TOKEN=$(cat ${KOKORO_KEYSTORE_DIR}/73713_yoshi-automation-github-key)
 
+# Install npm to facilitate installation of a code formatter for PHP: https://github.com/prettier/plugin-php
+# Use `nvm` to bootstrap the installation of node.js and npm.
+# To learn more: https://github.com/nvm-sh/nvm
+curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
+
+# Activate `nvm` so the binary is available on the path
+export NVM_DIR="$([ -z "${XDG_CONFIG_HOME-}" ] && printf %s "${HOME}/.nvm" || printf %s "${XDG_CONFIG_HOME}/nvm")"
+[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
+
+# Use the latest LTS version of nodejs.  This can change over time, but
+# should prevent the need to modify this file every year.
+nvm install --lts
+
+# Verify expected versions of nodejs and npm
+node --version
+npm --version
+
 # Setup git credentials
 echo "https://${GITHUB_TOKEN}:@github.com" >> ~/.git-credentials
 git config --global credential.helper 'store --file ~/.git-credentials'