[BUG] JSONPath文档错误

### 问题描述

JSONPath文档[FASTJSON2 JSONPath支持](https://alibaba.github.io/fastjson2/jsonpath_cn.html)介绍描述有误。示例1

```java
public void test_entity() throws Exception {
Entity entity = new Entity(123, new Object());

assertSame(entity.getValue(), JSONPath.eval(entity, "$.value"));
assertTrue(JSONPath.contains(entity, "$.value"));
assertTrue(JSONPath.containsValue(entity, "$.id", 123));
assertTrue(JSONPath.containsValue(entity, "$.value", entity.getValue()));
assertEquals(2, JSONPath.size(entity, "$"));
assertEquals(0, JSONPath.size(new Object[], "$"));
}
```
JSONPath无containsValue方法。

3.8 例8 keySet:

```java
// id is null, excluded by keySet
result = (Collection)JSONPath.eval(map, "$.e.keySet()");
assertEquals(1, result.size());
assertTrue(result.contains("name"));
```
not support syntax, path : $keySet()
JSONPathParser无keyset定义

```java
// Same result
assertEquals(result, JSONPath.keySet(map, "$.e"));
assertEquals(result, new JSONPath("$.e").keySet(map));
```
JSONPath无```keySet```方法