More documentation and examples

Can we please get some more documentation besides a schema and the super basic example in the README?

For example maybe

- further examples in the examples folder would help,
- for example an example of a complex custom element that covers all of the use cases,
- including all the `Type`s of usual attributes an element can have (number, string, boolean, etc), events (including `onfoo` properties, event types, etc),
- maybe examples of more complex types like `Array` in a recommended format (like a reference implementation) that people should try to follow
- How to generate CEM
- etc

Start with the schema, the basic README example, and the existing examples folder mentioned in the issue. Identify the current CEM generation guidance and decide which example cases are missing, including complex custom elements, attribute types, events, and complex types. Done means the requested documentation and representative examples are added with a clear recommended format.

Written by the indexing model from the issue text.