Implement utility function on the keyserver to upload notification payload to blob service

Summary:
This differential introduces utility function on the keyserver that AES-encrypts notification payload and uploads it to the keyserver. Changes in eslint configuration that are necessary for native node fetch API usage are introduced as
well.

Test Plan:

1. Launch blob service locally.
2. Modify blob-service.js file in facts directory to point to local IP address
3. Modify send.js file to execute this method on the stringified Android notification payload and log output to the console.
4. Send notification to Android device. Examine logs from keyserver and blob service terminals.

Reviewers: bartek, tomek, kamil

Reviewed By: bartek

Subscribers: michal, ashoat

Differential Revision: https://phab.comm.dev/D8529