* Create image-sizes.md
* adding thumbnail-image-regeneration.md
migrating thumbnail doc from wiki (https://github.com/woocommerce/woocommerce/wiki/Thumbnail-Image-Regeneration-in-3.3) so that the internal link can be updated in our image sizing document.
* Update image-sizes.md
* Update thumbnail-image-regeneration.md
* Update thumbnail-image-regeneration.md
We've been quietly building a set of documentation in a private repo that we are ready to move over to the public monorepo so that we can continue our initiative to imrpove the documentation experience for Woo developers.