stylecheck: add a check similar to ST1020, ST1021, ST1022 for struct field documentation

[ainar-g]

(I've searched the issue tracker, but it seems that this has never been brought up. If I'm wrong, feel free to close.)

package main

import "fmt"

// NotT is a type.
type T struct {
	// A is a field.
	A int

	// A is a field.
	B int
}

func main() {
	fmt.Println(T{})
}

staticcheck --version

staticcheck 2025.1 (0.6.0)

staticcheck --checks='*' ./main.go

• Got:

  main.go:5:1: comment on exported type T should be of the form "T ..." (with optional leading article) (ST1021)
  

• Expected:

  main.go:5:1: comment on exported type T should be of the form "T ..." (with optional leading article) (ST1021)
  main.go:10:2: comment on exported Field B should be of the form "B ..." (with optional leading article) (ST10XX)