I am using the basic EditorConfig configuration for XML files.
[*.{xml,xsd}]
max_line_length = off
end_of_line = lf
indent_style = space
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true
indent_size = 2
Since XML is so expressive I try to keep it tight with a indentation of only 2. At the same time I have disabled the maximum line length since XML in all it's expresiveness takes up a lot of room, so long lines and short indentation for readability.