Add Maven/Gradle usage examples to kotlinx-metadata-jvm ReadMe

libraries/kotlinx-metadata/jvm/ReadMe.md

@@ -2,6 +2,45 @@
 
 This library provides an API to read and modify metadata of binary files generated by the Kotlin/JVM compiler, namely `.class` and `.kotlin_module` files.
 
+## Usage
+
+To use this library in your project, add the kotlinx repository at https://kotlin.bintray.com/kotlinx, and a dependency on `org.jetbrains.kotlinx:kotlinx-metadata-jvm:$kotlinx_metadata_version` (where `kotlinx_metadata_version` is the version of the library).
+
+Example usage in Maven:
+
+```
+<project>
+    <dependencies>
+        <dependency>
+            <groupId>org.jetbrains.kotlinx</groupId>
+            <artifactId>kotlinx-metadata-jvm</artifactId>
+            <version>${kotlinx_metadata_version}</version>
+        </dependency>
+    </dependencies>
+    <repositories>
+        <repository>
+            <id>bintray-kotlin-kotlinx</id>
+            <name>bintray</name>
+            <url>https://kotlin.bintray.com/kotlinx</url>
+        </repository>
+    </repositories>
+    ...
+</project>
+```
+
+Example usage in Gradle:
+
+```
+repositories {
+    mavenCentral()
+    maven { url "https://kotlin.bintray.com/kotlinx/" }
+}
+
+dependencies {
+    compile "org.jetbrains.kotlinx:kotlinx-metadata-jvm:$kotlinx_metadata_version"
+}
+```
+
 ## Overview
 
 The entry point for reading the Kotlin metadata of a `.class` file is [`KotlinClassMetadata.read`](src/kotlinx/metadata/jvm/KotlinClassMetadata.kt). The data it takes is encapsulated in [`KotlinClassHeader`](src/kotlinx/metadata/jvm/KotlinClassHeader.kt) which is basically what is written in the [`kotlin.Metadata`](../../stdlib/jvm/runtime/kotlin/Metadata.kt) annotation on the class file generated by the Kotlin compiler. Construct `KotlinClassHeader` by reading the values from `kotlin.Metadata` reflectively or from some other resource, and then use `KotlinClassMetadata.read` to obtain the correct instance of the class metadata. (Note that loading values of `kotlin.Metadata` reflectively is only possible *from Java sources* until Kotlin 1.3, because this annotation is internal in the standard library, see [KT-23602](https://youtrack.jetbrains.com/issue/KT-23602).)