feat: detect missing `await` keyword and throw helpful error

[KnorpelSenf]

I just found the issue, seems like I forgor to use await on my next() middleware. Never thought the issue will be on middleware smh, since the code works without any wait() or waitFor().

Originally posted by @hanahaneull in https://github.com/grammyjs/conversations/issues/70#issuecomment-1438925401