Add an image of contributors at README.md

[vitormattos]

Solution description

An implementation example could be found here:

https://github.com/LimeSurvey/LimeSurvey

Documentation: https://contrib.rocks

If you have any other suggestion / idea about this feature, talk here first.

Additional context

This issue is open to contributors. If you're interested, feel free to leave a comment or open a draft PR to get started!

to-do

• Add the level 2 markdown header Contributors ✨
  example here
• After the new header and before the img, add the text Thanks go to these wonderful people:
  example here
• Add the img tag
  See the documentation
• Take a screenshot of README.md rendered with this feature and add to your pull request