add readme

README.md

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+# Daikon Prometheus
+
+![Daikon](./logo.svg)
+
+Daikon Prometheus is a library that add to Daikon the ability to expose metrics for Prometheus. 
+
+The main goals are:
+* Expose useful metrics for Prometheus
+
+## How to add Daikon Prometheus to your project
+[![](https://jitpack.io/v/DaikonWeb/daikon-prometheus.svg)](https://jitpack.io/#DaikonWeb/daikon-prometheus)
+
+### Gradle
+- Add JitPack in your root build.gradle at the end of repositories:
+```
+repositories {
+    ...
+    maven { url 'https://jitpack.io' }
+}
+```
+- Add the dependency
+```
+implementation('com.github.DaikonWeb:daikon-prometheus:1.1.8')
+```
+
+### Maven
+- Add the JitPack repository to your build file 
+```
+<repositories>
+    <repository>
+        <id>jitpack.io</id>
+        <url>https://jitpack.io</url>
+    </repository>
+</repositories>
+```
+- Add the dependency
+```
+<dependency>
+    <groupId>com.github.DaikonWeb</groupId>
+    <artifactId>daikon-prometheus</artifactId>
+    <version>1.1.8</version>
+</dependency>
+```
+
+## How to use
+
+### To publish metrics:
+```
+HttpServer()
+    .prometheus("/prometheus")
+    .start().use {
+        assertThat(get("http://localhost:4545/prometheus").text).contains("jvm")
+    }
+```
+
+### To use a custom metric:
+```
+HttpServer()
+    .prometheus("/prometheus")
+    .get("/counter") { _, _, ctx ->
+        ctx.meterRegistry().counter("calls").increment()
+    }
+    .start().use {
+        get("http://localhost:4545/counter")
+        get("http://localhost:4545/counter")
+        assertThat(get("http://localhost:4545/foo").text).contains("calls_total 2.0")
+    }
+```
+
+## Resources
+* Documentation: https://daikonweb.github.io
+* Examples: https://github.com/DaikonWeb/daikon-examples
+* Micrometer: https://micrometer.io/
+* Prometheus: https://github.com/prometheus
+
+## Authors
+
+* **[Daniele Fongo](https://github.com/danielefongo)**
+
+## License
+
+This project is licensed under the Apache License 2.0 - see the [LICENSE](LICENSE) file for details