Add .editorconfig

Helps with formatting files cross IDE/editor.

.editorconfig

@@ -5,7 +5,8 @@ charset = utf-8
 end_of_line = lf
 indent_size = 4
 indent_style = space
-insert_final_newline = false
+insert_final_newline = true
+trim_trailing_whitespace = true
 max_line_length = 120
 tab_width = 4
 ij_continuation_indent_size = 8