Add nvm for node management

Adding to the PHP images because certain WP-specific Grunt tasks rely on PHP,
so it makes sense to have it all in one place.

See also gitlab/ci/wordpress#1

php/8.0/Dockerfile

@@ -32,11 +32,15 @@ RUN docker-php-ext-install \
     && pecl install xdebug \
     && php -m
 
+ENV NVM_DIR /usr/local/nvm
+
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 RUN curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer \
     && chmod +x /usr/local/bin/composer \
     && composer --version \
+    && mkdir $NVM_DIR \
     && curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/master/install.sh | bash \
+    && . $NVM_DIR/nvm.sh \
     && nvm --version
 
 ENV PATH=/root/.composer/vendor/bin:$HOME/.composer/vendor/bin:$PATH