[FEATURE] Add .editorConfig Settings. [skip ci]

https://github.com/erlang/rebar3/issues/1443

.editorconfig

@@ -0,0 +1,13 @@
+# EditorConfig file: http://EditorConfig.org
+
+# Top-most EditorConfig file.
+root = true
+
+# Unix-style, newlines, indent style of 4 spaces, with a newline ending every file.
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 4