Make a few small amendments to editorconfig

Be explicit about encoding and line endings, and add the extra whitespace-on-empty-lines bit needed for Xcode to behave sensibly.

Author: jakepetroules

.editorconfig

@@ -1,7 +1,10 @@
 root = true
 
 [*]
+charset = utf-8
+end_of_line = lf
 indent_style = space
 indent_size = 2
 trim_trailing_whitespace = true
 insert_final_newline = true
+xcode_trim_whitespace_on_empty_lines = true