Add CHROME_BIN environment in Docker

- The upstream docker image uses Yarn, while I use npm and
  that screws up everything

Dockerfile

@@ -7,10 +7,14 @@ ARG VCS_REF
 
 WORKDIR /app
 
+# Ensure that the chromium path hasn't changed
+RUN ls /usr/local/share/.config/yarn/global/node_modules/puppeteer/.local-chromium/linux-650583/chrome-linux/chrome
+
 COPY package.json package-lock.json /app/
 
 RUN npm install
 
+
 LABEL org.label-schema.build-date=$BUILD_DATE \
       org.label-schema.name="Prometheus ACT Exporter" \
       org.label-schema.vcs-url="https://git.captnemo.in/nemo/prometheus-act-exporter.git" \
@@ -20,6 +24,8 @@ LABEL org.label-schema.build-date=$BUILD_DATE \
 
 COPY index.js server.js prom.js *.md /app/
 
+ENV CHROME_BIN="/usr/local/share/.config/yarn/global/node_modules/puppeteer/.local-chromium/linux-650583/chrome-linux/chrome"
+
 ENTRYPOINT ["/usr/local/bin/node", "server.js"]
 
 EXPOSE 3000