MaesterChestnut

Adding in a few flows for developers to try streaming, history, and image input quickly 

P0 - [x] Create menu/basic pulling from the existing menu section https://github.com/firebase/genkit/pull/57 - [x] Replace genkit init output with "menuSuggestionFlow" & modify documentation for Getting Started https://github.com/firebase/genkit/pull/62 - [ ]...