[Feat]: Add Documentation Comments

[Muhesh7]

In This PR

• Fixed the bug where loading Screen sometimes still keeps on loading even when the webView is loaded.
  - This is caused by an unhandled exception when the widget rebuilds itself
  Future is Completed Already
  - This is Fixed by adding a if check which checks if the future is completed already before calling the complete()
  if(!completer.isCompleted) completer.complete(true)
• Added Dart Documentation Comments for Every files.
  - This displays the description of a class or object when user Hovers his mouse on the class/methods.
• Updated the README.md with the newly refractor methods and Objects.