How to create a plugin for content area

I am new to Drupal. I want to create a plugin to extract and replace text from editing area(ckeditor).

Goal: Plugin should appear near ckeditor(not as a part of ckeditor toolbar) in a div.

The div should be able to load a webpage in a IFrame

Can anyone point to similar plugins are give an idea to startwith
 

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/4/feed