update aep-136 to clarify usage of kebab-case in the method name.

[toumorokoshi]

thanks! I think this change makes sense, but it will probably have to followed up with some clarification and corrections in https://aep.dev/136 as well. Specifically:

• we should clarify that custom methods should use kebab-case.
• fix the examples such as Stateless Methods, which use camelCase.

Originally posted by @toumorokoshi in #407 (comment)