Add: browser flag

[vaibhavsingh97]

Fixes: #12

• Added suggestion if user had passed wrong arguments.

• Added --browser flag will enable the user to pass the browser they wanted to add beforehand.
  Usage:

  npm init nightwatch -- --browser chrome --browser firefox
  # with alias
  npm init nightwatch -- -b chrome -b firefox
  # with yes flag and alias
  npm init nightwatch -- --yes -b chrome -b firefox

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Packages Added:

• Minimist for better package for argument parsing.

[garg3133]

Since to pass multiple browsers in argument, we need to write --browser multiple times (--browser chrome --browser edge) which is long, I think we should also have an alias for --browser. What about -b (-b chrome -b edge)?