Add "serve" or "preview" ability about guppy

[KyleAMathews]

People fairly regularly think Gatsby's development server is the same as a production site so write issues saying they don't understand why the JS bundle is so large, etc. So making the distinction between prod/development clear in Guppy's UI could help.

[joshwcomeau]

It'd be cool if after building your Gatsby or CRA site, you could then preview the built site via Gatsby's built-in serving and a standalone server for CRA.

Ahh, this is a great idea, and exactly the kind of neat benefit that a GUI allows for (well, could be done with a CLI too, but not without blocking that terminal window, so it can be much more unobtrusive with a UI)

I mentioned in #50 that I want to get rid of the "Tasks" module, where each task is identical row-to-row. This is a great example of how having a custom "Build" module would be preferable.

People fairly regularly think Gatsby's development server is the same as a production site so write issues saying they don't understand why the JS bundle is so large, etc. So making the distinction between prod/development clear in Guppy's UI could help.

Right, interesting. K, I'm excited about this direction. Just need to find the time to design and implement it.