fix missing example tag in documentation for color's toString method

[ashish1729]

Have not created an issue for this as it is a very small change

Changes:

The example code for toString method on p5.Color class was missing @example tag which was causing example code to show up as simple text, this PR fixes it.

Screenshots of the change:

• existing view
  
• after change
  

PR Checklist

• npm run lint passes
• Inline documentation is included / updated
• Unit tests are included / updated

[ashish1729]

I didn't create an issue because it is a tiny change but let me know if required.

[perminder-17]

Thanks for fixing this @ashish1729. LGTM :)

[Qianqianye]

Thanks @ashish1729 @perminder-17!

@all-contributors please add @ashish1729 for code

[allcontributors]

@Qianqianye

I've put up a pull request to add @ashish1729! 🎉