docs/bugpattern/PatternMatchingInstanceof.md

Pattern matching with `instanceof` allows writing this:

```java
void handle(Object o) {
  if (o instanceof Point(int x, int y)) {
    handlePoint(x, y);
  } else if (o instanceof String s) {
    handleString(s);
  }
}
```

which is more concise than an instanceof and a separate cast:

```java
void handle(Object o) {
  if (o instanceof Point) {
    Point point = (Point) o;
    handlePoint(point.x(), point.y());
  } else if (o instanceof String) {
    String s = (String) o;
    handleString(s);
  }
}
```

For more information on pattern matching and `instanceof`, see
[Pattern Matching for the instanceof Operator](https://docs.oracle.com/en/java/javase/21/language/pattern-matching-instanceof.html)