[Doc] Documentation Needed for eventmesh-connector-wechat

### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/eventmesh/issues?q=is%3Aissue) and found no similar issues.

### Documentation Related

Currently, most connectors lack documentation. The following details must be added to provide better clarity to the developers:
1. functions of the current connector
2. descriptions of configuration items
3. precautions (if any),
4. relevant official reference links (if any),
5. Other specific content that needs to be explained in the documentation.

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct) *

Start by locating the eventmesh-connector-wechat implementation and its configuration items. Review the connector behavior and existing project documentation, then document its functions, configuration descriptions, precautions, official references, and other needed details.

Written by the indexing model from the issue text.