Docs various updates (#2386)
To test:
> cd docs && make html
Changelogs:
* Added verbiage about the cap limit and data usage for the Freemium AP
* Added deprecated warning on Staging bricks
* Added warning and code examples to use the SaaS API Endpoints using
CLI-vs-SDKs
* Fixed example page formatting
* Added deprecation warning on ``model_name`` param in favor of
``hi_res_model_name``
* Added ``extract_images_in_pdf`` usage and code example in
``partition_pdf`` section
* Reorganized and improved the documentation Intro section
