UPDATE.md

Update instructions

drawio remote (onetime setup)

git remote add drawio https://github.com/jgraph/drawio.git

Version bump

git fetch rawio
git subtree -d pull -P "drawio" --squash -- drawio vXXXX
sed -i'' 's/"version": ".*"/"version": "'$(cat drawio/VERSION)'"/' package.json
git add package.json
git commit -m "Version bump to "$(cat drawio/VERSION)
git tag $(cat drawio/VERSION)
git push origin master $(cat drawiobatch/drawio/VERSION)