add an .editorconfig file to enforce the indentation/code style rules

.editorconfig

@@ -0,0 +1,16 @@
+# top-most EditorConfig file, enforcing some of the code style
+#
+# See http://editorconfig.org for a plugin to your editor!
+#
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[Makefile]
+indent_style = tab