Update SystemDS website with latest changes

[j143]

Instructions for my reference:

gitpod /workspace/systemds-website $ history
    1  git log
    2  git fetch https://github.com/apache/systemds master
    3  git fetch https://github.com/apache/systemds-website master
    4  git log
    5  git remote -v
    6  git remote add apache https://github.com/apache/systemds-website.git
    7  gulp
    8  npm install -g gulp
    9  gulp
   10  git checkout asf-staging
   11  git checkout -b update-website
   12  git log
   13  cp -r _site/* content/
   14  git add content/*
   15  git commit -m "Update SystemDS website with latest changes"
   16  git push https://github.com/j143/systemds-website 
   17  git push --set-upstream https://github.com/j143/systemds-website update-website
   18  git push -f --set-upstream https://github.com/j143/systemds-website update-website
   19  history