pack: add .editorconfig and use tab instead of space

.editorconfig

@@ -0,0 +1,11 @@
+# http://editorconfig.org
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = tab
+indent_size = 2
+insert_final_newline = true
+max_line_length = 80
+trim_trailing_whitespace = true