Add ATS Job APIs cheatsheet

[noble-ronin]

Description

Describe what changed and why it should be included.

Type of Change

• Add a new resource
• Update an existing resource
• Fix formatting/typos
• Improve categorization

Checklist

• I have read contributing.md.
• My change is specifically relevant to developer or engineer recruiting.
• I used the format [Name](URL) - Description. for list entries.
• I checked for duplicate entries.
• Descriptions are concise, objective, and end with a period.
• I verified links are valid and not broken.
• I used canonical HTTPS URLs without shorteners, referral codes, or tracking parameters.
• I disclosed any affiliation with the added/updated resource.
• This pull request contains a single logical change.

Additional Context

Add links, references, or screenshots if they help with review.

[CLAassistant]

All committers have signed the CLA.