Add Quadratic Solver (#2889)

README.md

@@ -1339,6 +1339,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Open Notify](http://open-notify.org/Open-Notify-API/) | ISS astronauts, current location, etc | No | No | Unknown |
 | [Open Science Framework](https://developer.osf.io) | Repository and archive for study designs, research materials, data, manuscripts, etc | No | Yes | Unknown |
 | [Purple Air](https://www2.purpleair.com/) | Real Time Air Quality Monitoring | No | Yes | Unknown |
+| [Quadratic Solver](https://quadratic-solver-api.herokuapp.com/) | A Quadratic Solver | No | Yes | Unknown |
 | [Satellite Passes](https://satellites.fly.dev) | Query next satellite passes above you | No | Yes | Yes |
 | [SHARE](https://share.osf.io/api/v2/) | A free, open, dataset about research and scholarly activities | No | Yes | Unknown |
 | [SpaceX](https://github.com/r-spacex/SpaceX-API) | Company, vehicle, launchpad and launch data | No | Yes | Unknown |