Deprecate Jquery

Jquery was included by default in Ember.js. Though it has served its purpose well, current state of ember and browsers no longer needs Jquery. Ember also has officially [deprecated Jquery](https://github.com/emberjs/rfcs/blob/master/text/0386-remove-jquery.md), we also wish to do the same.

Task: Remove all usages of jQuery throughout the project. One way to get started is to remove `@ember/jquery` package from package.json and re-rerun `yarn install` and check for errors due to absence of Jquery and fix them with suitable Vanilla JS / Ember code.

Start with package.json by removing the @ember/jquery package, then run yarn install and inspect the resulting errors for remaining jQuery usages. Replace those usages with suitable Vanilla JS or Ember code; done means the project no longer uses jQuery and installs without the reported errors.

Written by the indexing model from the issue text.