Add a feature for dark and light modes

[Omkaragrawal]

The feature will allow users to switch to dark or light mode as per their convenience, by default it should follow the browser mode.

[guptapranav4299]

I would like to work on this @Omkaragrawal

[Omkaragrawal]

@guptapranav4299 Make sure about these:

• The current UI HTML should be followed, keep in mind the ids, etc because those are referenced in the javascript for adding news feeds.

• UI for news feeds needs to be added in JS too, so update the html lines inside the js files, update them too according to UI.

The code of js is in assets/index.js.
Try using cdnjs for cdn purposes.
If you get any cors issue add the directives to server file and html file