Ability to script function add via cmd line params

**Is your feature request related to a problem? Please describe.**
It would be nice to have a headless way to add functions much like how init supports command line params now to provide automated options and better integration for compile to JS languages

**Describe the solution you'd like**
Ideal solution is something like `amplify function add --name foo -template hello-word`

**Describe alternatives you've considered**
I have tried building a CMD tool that just injects handles the fn add flow via Stdin but the timing is flakey and definitely not ideal. Another option might be to build a plugin that support it but it feels like it should just be baked into the flow that everyone is familiar with.

**Additional context**
The goal is provide build time macros via CLJS to handle a lot of the drudgery around adding lambda functions to the API as well automate steps that are easy to forget (adding the build line to the package.json scripts is somethin I always forget until the last minute).