Teleport imports #512

[perkee]

Solve issue #512. 100% AI written and I 100% understand if this goes nowhere. Making this binary my main driver for the next little while and if I like it, I'll take this out of draft.

• First commit is getting nix to work on my machine. Probably I'm holding it wrong and this should go Dropped because I had not rebased in far too long. Sorry
• first commit is the feature, including the plan, using this prompt:

   let's add a feature to elm-format whereby an import statement can appear on any line in a module and it will be moved to the import block. The best way to do this is to add a test wherein some imports appear
  after the top level declarations have started in the file. The test should assert that the output of running elm-format on such a file produces an elm file that compiles with the elm compiler. Create a plan in
  a markdown file including these steps and any intermediate steps, then iterate on the solution and check off the checklist in the markdown file.

• second commit the plan is deleted

Further commits are creating homebrew and nix packages for installing this as a binary