add a blog post about "CELLxGENE pseudobulk delivery via CuratedAtlasQuery"

[stemangiola]

@myushen will write a blog post about "CELLxGENE pseudobulk delivery via CuratedAtlasQuery"

@william-hutchison can support in case the "how to contribute" guidelines and not clear.

https://github.com/tidyomics/tidyomicsBlog/blob/master/CONTRIBUTING.md

This will also be an opportunity to improve the guidelines if needed.