Remove editorconfig layer

Since it does not bring anything to spacemacs
Use `dotspacemacs-additional-packages` instead to install it.

contrib/config/editorconfig/README.md

@@ -1,37 +0,0 @@
-# EditorConfig Layer for Spacemacs
-
-![EditorConfig](img/editorconfig.png)
-
-<!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc/generate-toc again -->
-**Table of Contents**
-
-- [EditorConfig Layer for Spacemacs](#editorconfig-layer-for-spacemacs)
-    - [Description](#description)
-    - [Install](#install)
-        - [Layer](#layer)
-        - [EditorConfig](#editorconfig)
-
-<!-- markdown-toc end -->
-
-## Description
-
-This layer provides support for [EditorConfig][].
-Syntax highlighting is also provided for `.editorconfig` files.
-
-## Install
-
-### Layer
-
-To use this contribution add it to your `~/.spacemacs`
-
-```elisp
-(setq-default dotspacemacs-configuration-layers '(editorconfig))
-```
-
-### EditorConfig
-
-If you have not installed the EditorConfig C Core already,
-follow the instructions [here][instructions].
-
-[EditorConfig]: http://editorconfig.org/
-[instructions]: https://github.com/editorconfig/editorconfig-core-c/blob/master/INSTALL.md

contrib/config/editorconfig/packages.el

@@ -1,6 +0,0 @@
-(setq editorconfig-packages '(editorconfig))
-
-(defun editorconfig/init-editorconfig ()
-  (use-package editorconfig
-    :defer t
-    :init (add-to-list 'auto-mode-alist '("\\.editorconfig" . conf-unix-mode))))