[FEATURE] Installation guide in README

[davayd]

🚀 Feature request

Is your feature request related to a problem?

What do you think about adding an installation section in README file? It would speed up the installation :) (Yeah, I prefer to copy these things)

Describe the solution you'd like

npm: npm install @ng-web-apis/common --save
yarn: yarn add @ng-web-apis/common
ng add: ng add @ng-web-apis/common@latest

[bboydflo]

Thanks for this library. I would like to also see a small example how to work with it in unit tests. I am not very familiar with angular