Context menu cytoscape plugin integration draft

[mj3cheun]

About

Adds ctxmenu plugin to dash-cytoscape

Pre-Merge checklist

• [ ] The project was correctly built with npm run build:all.
• [ ] If there was any conflict, it was solved correctly
• [ ] All changes were documented in CHANGELOG.md.
• [ ] All tests on CircleCI have passed.
• [ ] All Percy visual changes have been approved.
• [ ] Two people have :dancer:'d the pull request. You can be one of these people if you are a Dash Cytoscape core contributor.

Reference Issues

Closes #58