Update README with MCPs and API Gateway details

[aaguiarz]

Added new MCP resources and updated API Gateway section.

Description

What problem is being solved?

How is it being solved?

What changes are made to solve it?

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[Copilot]

Pull Request Overview

This PR updates the README to better organize MCP (Model Context Protocol) resources and expand the API Gateway section with additional tools.

• Reorganizes MCP resources into a dedicated section with clearer categorization
• Adds new MCP servers including remote server and additional tools
• Expands API Gateway section to include proxies and adds Heimdall integration

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