Print a message when done fetching deps (elixir-editors#380)

* Print a message when done fetching deps

Otherwise the user doesn't know when the server is done, and running a
command like "mix deps.get" at the same time is the server can result in
corrupted files.

* Fix formatting

Author: axelson

apps/language_server/lib/language_server/build.ex

@@ -238,6 +238,11 @@ defmodule ElixirLS.LanguageServer.Build do
       )
 
       Mix.Task.run("deps.get")
+
+      JsonRpc.show_message(
+        :info,
+        "Done fetching deps"
+      )
     end
 
     :ok