Fixed yarn not installing node packages for streaming (#27967)

Dockerfile

@@ -38,6 +38,7 @@ RUN apt-get update && \
     corepack enable
 
 COPY Gemfile* package.json yarn.lock .yarnrc.yml /opt/mastodon/
+COPY streaming/package.json /opt/mastodon/streaming/
 COPY .yarn /opt/mastodon/.yarn
 
 RUN bundle install -j"$(nproc)"