Add editorconfig file.

Author: Crell

.editorconfig

@@ -0,0 +1,15 @@
+; This file is for unifying the coding style for different editors and IDEs.
+; More information at http://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+indent_size = 4
+indent_style = space
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[Makefile]
+indent_style = tab