Explanation for Servant

[iluwatar]

In this issue, let's add a proper explanation for the pattern.

Acceptance criteria

• The pattern's README.md has been amended with an explanation
• The explanation consists of
  • Real world example
  • In plain words
  • Wikipedia says
  • Programmatic example

[mm-saiful6854]

Hello. I want to nominate myself for writing explanation about Servant design pattern.

[ved-asole]

Hi @iluwatar, I would like to take care of the above feature. Please assign it to me.