Remove the reactor #4
Description
The reactor is a builtin web-server which makes it easy to run a Elm file in a browser, and have it be automaticly updated whenever the source changes.
While the reactor is good to have for people new to Elm, as it let's them get started quickly, I've personally only used it once or twice. In every serious project I've always used a tool such as parcel or webpack to run my Elm code. Even when teaching, I've provided my audience with a quick-start git repo with a completed parcel setup.
The reactor includes an Elm project, which means that to be able to support the reactor in Gren, we'd need to port all those dependencies before a first release.
Because of these reasons, I opt to remove the reactor from the Gren compiler. It can be added back in a later release if there's need for it.
As an extra benefit, we should be able to remove the included web-server, which should make our compiler smaller.