[Feature Request]: AWS AppSync & AppSync Events API

### Describe the feature

Add Skills etc., for [AWS AppSync](https://aws.amazon.com/appsync/resources/) & newer [AppSync Events API](https://docs.aws.amazon.com/appsync/latest/eventapi/event-api-welcome.html). Covering both frontend & backend usage - preferably both with and without Amplify Client. Currently there's only brief mentions across other generic and specialized skills but those mentions route to literally nothing because there are no skills for AppSync & AppSync Events API. (i.e. [core:launch-with-aws](https://github.com/aws/agent-toolkit-for-aws/blob/d6ad2e44d5e3077b85b63f322e007c84f94f3a6c/skills/core-skills/launch-with-aws/SKILL.md?plain=1#L75))

From personal experience the overall AppSync Events documentation/coverage is filled with erroring/unsafe (ts) examples when implemented, and most useful material hidden behind obscure/undiscoverable articles in a mobile section of the website. (i.e. https://aws.amazon.com/blogs/mobile/working-with-aws-appsync-events-real-time-web-games-with-chat/)

AppSync/AppSync Events especially, need much more care and effort put into its documentation and actually be supported in Agent Toolkit.

### Use Case

Maximize efficiency and correctness with agentic development. Using AppSync/Events API, important patterns, usage with AWS CDK, TypeScript usage, examples/usage with both popular and modern libraries like React, TanStack Query, etc, with & without Amplify Client.

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

Start with skills/core-skills/launch-with-aws/SKILL.md, where the existing AppSync reference currently routes to no skill, then review the linked AppSync and AppSync Events resources. Done means adding useful coverage for frontend and backend usage, with and without Amplify Client, including the requested TypeScript, CDK, and library patterns.

Written by the indexing model from the issue text.