chore: import upstream snapshot with attribution

docs/api/restful_java.md

@@ -0,0 +1,21 @@
+# Java RESTful API
+
+Add the following dependency into the `pom.xml` file of your project. 
+
+```xml
+<dependency>
+  <groupId>com.hankcs.hanlp.restful</groupId>
+  <artifactId>hanlp-restful</artifactId>
+  <version>0.0.15</version>
+</dependency>
+```
+
+Obtain an `auth` from any compatible service provider like our [free service](https://bbs.hankcs.com/t/apply-for-free-hanlp-restful-apis/3178), then initiate a `HanLPClient` and call its `parse` interface.
+
+```java
+HanLPClient client = new HanLPClient("https://hanlp.hankcs.com/api", null); // Replace null with your auth
+System.out.println(client.parse("2021年HanLPv2.1为生产环境带来次世代最先进的多语种NLP技术。晓美焰来到北京立方庭参观自然语义科技公司。"));
+```
+
+Refer to our [testcases](https://github.com/hankcs/HanLP/blob/master/plugins/hanlp_restful_java/src/test/java/com/hankcs/hanlp/restful/HanLPClientTest.java) and [data format](../data_format) for more details.
+