Define editorconfig file

This file can be used by editors and IDEs to determine whitespace
usage within a file. Line-endings, tabs vs spaces, etc are defined.

I set this file up so that the PHP files are use PSR-2 whitespaces.

.editorconfig

@@ -0,0 +1,22 @@
+# See http://EditorConfig.org for more information
+
+# top-most EditorConfig file
+root = true
+
+# Every File
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+charset = utf-8
+indent_style = space
+indent_size = 4
+
+[*.{yml,md}]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.twig]
+insert_final_newline = false