Create CONTRIBUTING.md file

[victorhmp]

What is the purpose of this pull request?

Finally creating a CONTRIBUTING.md file for all Store Framework repos 🙌🏻 .

Here you can check the rendered version: https://github.com/vtex-apps/store-discussion/blob/feat/contributing/CONTRIBUTING.md

[vtex-io-docs-bot[bot]]

Beep boop :robot:

I noticed you're not using the Docs Builder properly yet, if you need help to set that up please go to IO Documentation

[vtex-io-ci-cd[bot]]

Hi! I'm VTEX IO CI/CD Bot and I'll be helping you to publish your app! 🤖

Please select which version do you want to release:

• [ ] Patch (backwards-compatible bug fixes)

• [x] Minor (backwards-compatible functionality)

• [ ] Major (incompatible API changes)

And then you just need to merge your PR when you are ready! There is no need to create a release commit/tag.

• [ ] No thanks, I would rather do it manually 😞