Added docker deployment

Author: JStumpp

md/docker.md

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+# docker
+
+Docker is the world’s leading software containerization platform. You can easily run you Jooby app as a docker container. You need to have the docker engine [installed](https://docs.docker.com/engine/installation/).
+
+## usage
+
+You need [docker](https://docs.docker.com/engine/installation/) installed on the building machine.
+
+Add the following to the pom.xml under plugins:
+
+```xml
+<plugin>
+    <groupId>com.spotify</groupId>
+    <artifactId>docker-maven-plugin</artifactId>
+    <version>0.4.13</version>
+    <configuration>
+        <imageName>my-jooby-image</imageName>
+        <baseImage>openjdk:jre-alpine</baseImage>
+        <entryPoint>["java", "-jar", "/${project.build.finalName}.jar"]</entryPoint>
+        <exposes>
+          <expose>8080</expose>
+        </exposes>
+        <resources>
+            <resource>
+                <targetPath>/</targetPath>
+                <directory>${project.build.directory}</directory>
+                <include>${project.build.finalName}.jar</include>
+            </resource>
+        </resources>
+    </configuration>
+</plugin>
+ ```
+
+In order to create the **docker image** go to your project home, open a terminal and run:
+
+```bash
+mvn clean docker:build
+```
+
+Once it finish, the docker image will be build and tagged as ```my-jooby-image```.
+
+## run / start
+
+You can now run the image with:
+
+```bash
+docker run -p 80:8080 my-jobby-image
+```