Add interesting features 🌟

[sahilrajput03]

Add support for running
1.) Custom start command before running the task via start option (inspired from nodemon's api)
2.) Clear logs before every run of change files in the task event via clearOnStart option

So for adding those two options looks like:

module.exports = {
	// ...
	  watcher: {
		  mycontracts: {
			  clearOnStart: true,
			  start: 'echo Staring my Sweet testing now!',
			  // ...
		  },
		  // ...
	  },
}

Thanks. I hope users of of this lib will like it as well.

[sahilrajput03]

@xanderdeseyn , does this PR looks good to you?

[xanderdeseyn]

I can look at it this week!

[xanderdeseyn]

Can you add some docs to the readme as well please?

[sahilrajput03]

@xanderdeseyn , sure!

[sahilrajput03]

Please review the changes I made in readme file here in the PR diff.

[xanderdeseyn]

Thanks for the contribution!

[sahilrajput03]

awesome!. Thanks for considering my code.