feat: add middlewares for handler

[TBXark]

Sometimes it is necessary to add middleware for individual handlers.

I added an example in the example, for instance, sometimes when we handle CallbackQuery, it may not be so quick, and users may click the button multiple times, resulting in multiple requests arriving simultaneously. At this point, we can use singleFlight to ensure that only one request is processed.

[TBXark]

The addition of m ...Middleware to the RegisterHandlerXXX function signature will not affect the execution of the previous code, because m is a variadic parameter with a default value of empty, so the previous code will not be impacted.