ST1021: structs named `A` do not have their proper documentation recognized.

```go
package main

// A does foo.
type A struct{}

func main() {
	var a A
	println(a)
}
```

```
junk.go:3:1: ST1021: comment on exported type A should be of the form "A ..." (with optional leading article) (stylecheck)
// A does foo.
```