Create Provider Documentation Page for OpenAI

Problem/Motivation

Currently there is no information about providers on https://project.pages.drupalcode.org/ai, except for https://project.pages.drupalcode.org/ai/1.1.x/providers/matris/

This makes it hard to know what to choose, why and how to set it up.

We need detailed pages for each provider that we manage, or that is known to the community, so there is one place to look for information about what to use and where to use it.

This task is for createing the OpenAI details documentation page.

Proposed resolution

• Write a summary of 2-3 sentences of what the provider does, and why you should choose it. This will be used on overview pages as well. Under the headline Summary.
• Write a longer description of the provider if wanted under the headline Description. This can be information about specific models, operation types or other information that might be important.
• Write an installiation description under the headline Installation. For OpenAI this should be fairly short. For a provider like Google Vertext, this might be under sections as well.
• Write a reference section with links to get more information about the provider with the headline More Information. In OpenAI's case this should link to registration, pricing page and platform at least.
• All headlines should be h2, unless they are subsections.
• For any logo that needs to be provided, please give it to a maintainer to upload in the wiki. Do not push it into the repo, we do not want a large filesize on the repo history.

Since this is the first issue like this, please discuss if something is missing in this template. Then it can be used to copy for each of the provider. We want to give incentives to write documentation, so it will be one credit per page.