add example with struct literal

Co-authored-by: Josh Triplett <josh@joshtriplett.org>

Author: pitaj

src/doc/style-guide/src/expressions.md

@@ -841,6 +841,11 @@ let x = format!("Stuff: {}", [
     an_expr,
     another_expr,
 ]);
+
+let x = func(an_expr, another_expr, SomeStruct {
+    field: this_is_long,
+    another_field: 123,
+});
 ```
 
 Apply this behavior recursively.