Blog on Complex Types

- Part of https://github.com/apache/parquet-site/issues/146

The way Parquet handles nested types using the dremel shredding model can be somewhat confusing

It would be nice to have a blog post on https://parquet.apache.org/blog/ with a high level
1. Explain the usecase of complex types types (and how it varies from Variant, for example)
2. Gives a technical overview of the types (e.g. how they are stored)

Review the related issue at https://github.com/apache/parquet-site/issues/146 and the blog location at https://parquet.apache.org/blog/. Research Parquet complex types, their use cases versus Variant, and how they are stored using the Dremel shredding model. Done means a high-level blog post covers both the conceptual and technical overviews.

Written by the indexing model from the issue text.