feat(docs): add how to add custom plugin to docker image

content/docs/02.installation/02.docker.md

@@ -62,6 +62,19 @@ RUN mkdir -p /app/plugins && \
 
 ### Add plugins to a Docker image
 
+If you are developing a custom plugins, you will need at first to [build it](../09.plugin-developer-guide/08.build.md). Once the shadowJar is build, you just to copy this one inside the plugin's directory:
+
+```dockerfile
+ARG IMAGE_TAG=latest
+FROM kestra/kestra:$IMAGE_TAG
+
+RUN mkdir -p /app/plugins
+
+COPY /build/libs/*.jar /app/plugins
+```
+
+### Add a custom plugins to a Docker image
+
 By default, the base Docker image `kestra/kestra:latest` does not contain any plugins (unless you use the `kestra/kestra:latest-full` version). You can add the needed plugins to the base image and build a custom image.
 
 The following `Dockerfile` creates an image from the base image and adds the `plugin-notifications`, `storage-gcs` and `plugin-gcp` binaries using the command `kestra plugins install`: