### What it does
This lint warns about the use of literals as `write!`/`writeln!` args.

### Why is this bad?
Using literals as `writeln!` args is inefficient
(c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
(i.e., just put the literal in the format string)

### Example
```
writeln!(buf, "{}", "foo");
```

Use instead:
```
writeln!(buf, "foo");
```