Missing mock files leads to failed tests

[wwang107]

Test is failing every time because static resources, such as .png, can not be imported properly in Jest. For example, in the build pipeline, one can see the error message

Test suite failed to run

    Configuration error:
    
    Could not locate module ../../assets/images/hyf-logo.png mapped as:
    /Users/wwang/Guide-IT/__mocks__/fileMock.js.
    
    Please check your configuration for these entries:
    {
      "moduleNameMapper": {
        "/\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$/": "/Users/wwang/Guide-IT/__mocks__/fileMock.js"
      },
      "resolver": null
    }

To address the issue, mockFile.js need to be created.

jestjs/jest#2663

https://stackoverflow.com/questions/46898638/importing-images-breaks-jest-test

Acceptance criteria
Mock the static files properly, so the mentioned error message is gone.