Add Readme templates.

See spring-projects/spring-data-build#2758

Author: mp911de

.github/README.template.adoc

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+= Spring Data for Elasticsearch image:https://jenkins.spring.io/buildStatus/icon?job=spring-data-elasticsearch%2Fmain&subject=Build[link=https://jenkins.spring.io/view/SpringData/job/spring-data-elasticsearch/] https://gitter.im/spring-projects/spring-data[image:https://badges.gitter.im/spring-projects/spring-data.svg[Gitter]] image:https://img.shields.io/badge/Revved%20up%20by-Develocity-06A0CE?logo=Gradle&labelColor=02303A["Revved up by Develocity", link="https://ge.spring.io/scans?search.rootProjectNames=Spring Data Elasticsearch"]
+
+The primary goal of the https://projects.spring.io/spring-data[Spring Data] project is to make it easier to build Spring-powered applications that use new data access technologies such as non-relational databases, map-reduce frameworks, and cloud based data services.
+
+The Spring Data Elasticsearch project provides integration with the https://www.elastic.co/[Elasticsearch] search engine.
+Key functional areas of Spring Data Elasticsearch are a POJO centric model for interacting with Elasticsearch Documents and easily writing a Repository style data access layer.
+
+This project is lead and maintained by the community.
+
+== Features
+
+* Spring configuration support using Java based `@Configuration` classes or an XML namespace for an ES client instances.
+* `ElasticsearchOperations` class and implementations that increases productivity performing common ES operations.
+Includes integrated object mapping between documents and POJOs.
+* Feature Rich Object Mapping integrated with Spring’s Conversion Service
+* Annotation based mapping metadata
+* Automatic implementation of `Repository` interfaces including support for custom search methods.
+* CDI support for repositories
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/code-of-conduct.adoc[]
+
+== Getting Started
+
+Here is a quick teaser of an application using Spring Data Repositories in Java:
+
+[source,java]
+----
+public interface PersonRepository extends CrudRepository<Person, Long> {
+
+  List<Person> findByLastname(String lastname);
+
+  List<Person> findByFirstnameLike(String firstname);
+}
+
+@Service
+public class MyService {
+
+  private final PersonRepository repository;
+
+  public MyService(PersonRepository repository) {
+    this.repository = repository;
+  }
+
+  public void doWork() {
+
+    repository.deleteAll();
+
+    Person person = new Person();
+    person.setFirstname("Oliver");
+    person.setLastname("Gierke");
+    repository.save(person);
+
+    List<Person> lastNameResults = repository.findByLastname("Gierke");
+    List<Person> firstNameResults = repository.findByFirstnameLike("Oli");
+ }
+}
+----
+
+=== Using the RestClient
+
+Please check the https://docs.spring.io/spring-data/elasticsearch/docs/current/reference/html/#elasticsearch.clients.configuration[official documentation].
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/dependencies.adoc[]
+
+**Compatibility Matrix**
+
+The compatibility between Spring Data Elasticsearch, Elasticsearch client drivers and Spring Boot versions can be found in the https://docs.spring.io/spring-data/elasticsearch/docs/current/reference/html/#preface.versions[reference documentation].
+
+To use the Release candidate versions of the upcoming major version, use our Maven milestone repository and declare the appropriate dependency version:
+
+[source,xml]
+----
+<dependency>
+  <groupId>org.springframework.data</groupId>
+  <artifactId>spring-data-elasticsearch</artifactId>
+  <version>${version}.RCx</version> <!-- x being 1, 2, ... -->
+</dependency>
+----
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/getting-help.adoc[]
+
+include::https://raw.githubusercontent.com/spring-projects/spring-data-build/refs/heads/main/etc/readme/license.adoc[]
+