Add Config Flag to disable shiny

[LukvonStrom]

First of all, thank you, dear AWS Team for this great repo!
I just wanted to request a more or less complicated switch in the cdk.json, to not deploy Shiny.
This reduces some cost for usecases, where Shiny is not needed and thus excess infrastructure.

Thanks in advance for considering to implement this!

/cc @pchayan

[pchayan]

Thanks @LukvonStrom , we can include a flag not to install Shiny if Shiny is not needed. Sometime next week.