Add a(n) `.editorconfig` file

part of the broken formatting changes

.editorconfig

+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 4
+indent_style = space
+insert_final_newline = false
+max_line_length = 120
+tab_width = 4
+trim_trailing_whitespace = true