Add AGENTS.md and related links (CLAUDE.md, GEMINI.md) to allow code generation tools to interact with the operator-framework/operator-marketplace repository.

The document may detail information useful to agents such as patterns, conventions and architectural decisions while avoiding overly specific implementation details.

Consider adding information like:

• table of contents
• description
• architectural details (components, directory structure)
• Common workflows (setup, building, testing, validation/linting, vendor/dependency management, code generation, commit creation, PR creation etc.)
• development conventions (code style, PR/commit formats, contribution guidelines, backporting guidelines, safety/security guidelines, etc)
• debugging steps for common errors

Some sample AGENTS.md for reference:

• operator-framework-olm/operator-lifecycle-manager
• operator-framerwork-olm/operator-registry
• operator-framework-olm/tests-extension
• operator-framework/api
• openshift/kubernetes
• kubernetes/kubernetes
• agents.md official samples