Add documentation to README

This commit adds some documentation to the README file:

* getting started with this project
* core auto-configuration
* metrics support

README.md

@@ -2,6 +2,156 @@
 
 Experimental project to create [GraphQL](https://graphql.org/) support for Spring applications.
 
+[![Build status](https://ci.spring.io/api/v1/teams/spring-graphql/pipelines/spring-graphql/jobs/build/badge)](https://ci.spring.io/teams/spring-graphql/pipelines/spring-graphql)
+
+
+## Getting started
+
+This project is tested against Spring Boot 2.4+, but should work on 2.3 as well.
+
+You can start by creating a project on https://start.spring.io and select the `spring-boot-starter-web` or `spring-boot-starter-webflux` starter,
+depending on the type of web application you'd like to build. Once the project is generated, you can manually add the
+`org.springframework.experimental:spring-graphql-web` dependency.
+
+`build.gradle` snippet:
+```groovy
+dependencies {
+    implementation 'org.springframework.experimental:spring-graphql-web:0.1.0-SNAPSHOT'
+    
+    // Spring Web MVC starter
+    implementation 'org.springframework.boot:spring-boot-starter-web'
+    // OR Spring WebFlux starter
+    implementation 'org.springframework.boot:spring-boot-starter-webflux'
+
+} 
+
+repositories {
+    mavenCentral()
+    // don't forget to add spring milestone and snapshot repositories
+    maven { url 'https://repo.spring.io/milestone' }
+    maven { url 'https://repo.spring.io/snapshot' }
+}
+``` 
+
+`pom.xml` snippet:
+```xml
+<dependencies>
+    <dependency>
+        <groupId>org.springframework.experimental</groupId>
+        <artifactId>spring-graphql-web</artifactId>
+        <version>0.1.0-SNAPSHOT</version>
+    </dependency>
+    
+    <!-- Spring Web MVC starter -->
+    <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-web</artifactId>
+    </dependency>
+    <!-- OR Spring WebFlux starter -->
+    <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-webflux</artifactId>
+    </dependency>
+    <!-- ... -->
+</dependencies>
+
+<repositories>
+    <repository>
+        <id>spring-milestones</id>
+        <name>Spring Milestones</name>
+        <url>https://repo.spring.io/milestone</url>
+    </repository>
+    <repository>
+        <id>spring-snapshots</id>
+        <name>Spring Snapshots</name>
+        <url>https://repo.spring.io/snapshot</url>
+        <snapshots>
+            <enabled>true</enabled>
+        </snapshots>
+    </repository>
+</repositories>
+```
+
+You can now add a GraphQL schema in `src/main/resources/schema.graphqls` such as:
+
+```
+schema {
+    query: QueryType
+}
+
+type QueryType {
+    people: [Person]!
+}
+
+type Person {
+    id: ID!
+    name: String!
+}
+```
+
+And then you should configure the data fetching using a `RuntimeWiringCustomizer` and custom components like
+Spring Data repositories, `WebClient` instances for Web APIs, a `@Service` bean, etc. 
+
+```java
+@Component
+public class PersonDataWiring implements RuntimeWiringCustomizer {
+
+	private final PersonService personService;
+
+	public PersonDataWiring(PersonService personService) {
+		this.personService = personService;
+	}
+
+	@Override
+	public void customize(RuntimeWiring.Builder builder) {
+		builder.type("QueryType", typeWiring -> typeWiring
+				.dataFetcher("people", env -> this.personService.findAll()));
+	}
+}
+```
+
+You can now start your application!
+A GraphiQL web interface is available at `http://localhost:8080/graphql` and you can use GraphQL clients
+to POST queries at the same location.
+
+
+## Features
+
+### Core configuration
+The Spring GraphQL project offers a few configuration properties to customize your application: 
+
+````properties
+# web path to the graphql endpoint
+spring.graphql.path=/graphql
+# location of the graphql schema file
+spring.graphql.schema-location=classpath:/schema.graphqls
+# Whether micrometer metrics should be collected for graphql queries
+management.metrics.graphql.autotime.enabled=true
+````
+
+You can contribute `RuntimeWiringCustomizer` beans to the context in order to configure the runtime wiring of your GraphQL application.
+
+### Metrics
+
+If the `spring-boot-starter-actuator` dependency is on the classpath, metrics will be collected for GraphQL queries.
+You can see those metrics by exposing the metrics endpoint with `application.properties`:
+```properties
+management.endpoints.web.exposure.include=health,metrics,info
+```
+
+You can then check those metrics at `http://localhost:8080/actuator/metrics/graphql.query`.
+
+
+## Sample application
+
+This repository contains a sample application that the team is using to test new features and ideas.
+
+You can run it by cloning this repository and typing on the command line:
+
+```shell script
+$ ./gradlew :graphql-sample:bootRun
+```
+
 
 ## License