NoMongo: Fix Stylesheet in Anticipation of Dark Mode

[palisadoes]

A simple "search and replace" is not enough. Please read carefully

Is your feature request related to a problem? Please describe.

1. We will eventually implement a Light / Dark Mode option in the Web UI
2. To make this easier we need to review the single CSS style sheet to remove references to colors and replace them with the role of the color in components or screens. For example:
   1. Instead of --red-delete-bg use --delete-button-bg
   2. Instead of --red-delete-text use --delete-button-text
   3. Instead of --blue-primary use a name that describes the role of the color like --margin-color-for-xxxxxxxx where xxxxxxx is the component
3. This will mean that you'll have to go through all the use cases for each color and add additional variables with the same or different colors according to the role. For example:
   1. References to --brown-color occur 25 times in different roles in different screens and components.
   2. References to --light-dark-green occur 3 times in similar situations. The role in different screens and components should be used instead.
   3. References to --black-color occur 36 times in similar situations. The role in different screens and components should be used instead.
4. In the end there must be no references to colors, only to roles. Therefore when we add a new app-dark.module.css file for Dark Mode the process will be much easier.
5. The CSS file can be found here
   1. https://github.com/PalisadoesFoundation/talawa-admin/blob/main/src/style/app.module.css.

Additional context

Potential internship candidates

Please read this if you are planning to apply for a Palisadoes Foundation internship

• Student Internship Programs talawa#359

[AQIB-NAWAB]

Hy @palisadoes, can i work on this issue ?

[palisadoes]

Also remove any references that are unused