Add datamodel code generator python code

[denisart]

Description

I added tool for data model generation from a GraphQL schema for python: datamodel-code-generator.

docs: https://koxudaxi.github.io/datamodel-code-generator/ source: https://github.com/koxudaxi/datamodel-code-generator pypi: https://pypi.org/project/datamodel-code-generator/

[gatsby-cloud[bot]]

:x: graphql.github.io-source deploy preview failed

Your build failed. View the build logs.

[saihaj]

hey @denisart can you rebase this PR? I can help land the changes.