Update compose-structs.md

[detoxifiedplant]

change in indentation & styling for better reading

[marcoieni]

thanks!

[marcoieni]

Can you find a solution to fix dprint?

E.g. we could use the ^^^ also for the other comment?

[marcoieni]

Something like this:

    print_database(&db); 
    //              ^^ Immutable borrow of `db` happens here
    // *connection_string = "new string".to_string();
    // ^^^^^^^^^^^^^^^^^^ Mutable borrow is used here

[detoxifiedplant]

@marcoieni sure, let me see what can be done to fix it