Simple demo of shared cursors, presence, Quill etc

To run (after installing parcel globally)

``
yarn install
node server.js &
parcel src/index.html
``

Custom packages:

- this demo: https://github.com/houshuang/react-demo
- @chilifrog/reactive-tools: https://github.com/chili-epfl/FROG#reactive-tools
- @chilifrog/sharedb: https://github.com/houshuang/sharedb (based on @teamwork fork)
- @chilifrog/sharedb-mongo https://github.com/houshuang/sharedb-mongo (based on @teamwork fork, just added different sharedb)
- @houshuang/react-quill https://github.com/houshuang/react-quill
- @minervaproject/ot-json0 https://github.com/houshuang/json0#curran
- @minervaproject/quill-cursors https://github.com/houshuang/quill-cursors (added flashing)
- @minervaproject/rich-text https://github.com/houshuang/rich-text#teamwork-sharedb-presence