docs(troubleshooting): install libXss in Dockerfile (#6236)

The new version of chromium requires libxss.

docs/troubleshooting.md

@@ -256,7 +256,7 @@ To fix, you'll need to install the missing dependencies and the
 latest Chromium package in your Dockerfile:
 
 ```Dockerfile
-FROM node:10-slim
+FROM node:12-slim
 
 # Install latest chrome dev package and fonts to support major charsets (Chinese, Japanese, Arabic, Hebrew, Thai and a few others)
 # Note: this installs the necessary libs to make the bundled version of Chromium that Puppeteer
@@ -266,7 +266,7 @@ RUN apt-get update \
     && wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - \
     && sh -c 'echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list' \
     && apt-get update \
-    && apt-get install -y google-chrome-unstable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf \
+    && apt-get install -y google-chrome-unstable fonts-ipafont-gothic fonts-wqy-zenhei fonts-thai-tlwg fonts-kacst fonts-freefont-ttf libxss1 \
       --no-install-recommends \
     && rm -rf /var/lib/apt/lists/*