Add editorconfig for code conventions

This is a widely used file that instructs editors about which settings to use. Won't help in every case but it is a baseline.

.editorconfig

@@ -0,0 +1,12 @@
+# EditorConfig helps developers define and maintain consistent
+# coding styles between different editors and IDEs
+# editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true