feat: Add ctx.has

[KnorpelSenf]

This should be a namespace to query the context object for certain properties, such as whether it contains a command or not.

Once added, this can be reused in the composer, hence improving SoC internally in the library.

[KnorpelSenf]

It would also be good to have a static Context.has which compiles predicate functions that can be checked fast. Currently, the composer does these things internally, so if we move the checks for each context object, we lose the performance optimisations. Hence, by exposing them statically and re-using these things in the composer, we obtain code with equivalent complexity and constants, while still having a cleaner separation of concerns and better reusability for conversations.