As i remember you can’t install repository from github in anyway. But you can up your own server in react and create relationship with your bubble.io app.
That library is already published on npm and you can use it without forking it.
Are you using a fork because you plan to modify the code? Try "ics": "github:Field-Day-CI/ics"
It appears that bubble’s infra doesn’t support git when installing the packages for ssa.
You can ask the support if they can confirm this.
In the meantime you can publish your fork on npm and use it.
change the name in the package.json to something like your-npmjs-username@ics so that you publish the package under your username scope and avoid conflicting names