docs: Add Linux install instructions

Signed-off-by: Christopher Crone <christopher.crone@docker.com>
Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

ecs/docs/get-started-linux.md

@@ -0,0 +1,84 @@
+Getting Started with Docker AWS ECS Plugin Beta on Linux
+--------------------------------------------------------
+
+The beta release of [AWS ECS](https://aws.amazon.com/ecs/) support for the
+Docker CLI is shipped as a CLI plugin. Later releases will be included as part
+of the Docker CLI.
+
+This plugin is included as part of Docker Desktop on Windows and macOS but on
+Linux it needs to be installed manually.
+
+## Prerequisites
+
+* [Docker 19.03 or later](https://docs.docker.com/get-docker/)
+
+## Step by step install
+
+### Download
+
+You can download the Docker ECS plugin from this repository using the following
+command:
+
+<!-- FIXME(chris-crone): get real download link -->
+```console
+$ curl -L http://xxx | tar xzf -
+```
+
+You will then need to make it executable:
+
+```console
+$ chmod +x docker-ecs
+```
+
+### Plugin install
+
+In order for the Docker CLI to use the downloaded plugin, you will need to move
+it to the right place:
+
+```console
+$ mkdir -p /usr/local/lib/docker/cli-plugins
+
+$ mv docker-ecs /usr/local/lib/docker/cli-plugins/
+```
+
+You can put the CLI plugin into any of the following directories:
+
+* `/usr/local/lib/docker/cli-plugins`
+* `/usr/local/libexec/docker/cli-plugins`
+* `/usr/lib/docker/cli-plugins`
+* `/usr/libexec/docker/cli-plugins`
+
+Finally you need to enable the experimental features on the CLI. This can be
+done by setting the environment variable `DOCKER_CLI_EXPERIMENTAL=enabled` or by
+setting `experimental` to `"enabled"` in your Docker config found at
+`~/.docker/config.json`:
+
+```console
+$ export DOCKER_CLI_EXPERIMENTAL=enabled
+
+$ DOCKER_CLI_EXPERIMENTAL=enabled docker help
+
+$ cat ~/.docker/config.json
+{
+  "experimental" : "enabled",
+  "auths" : {
+    "https://index.docker.io/v1/" : {
+
+    }
+  }
+}
+```
+
+To verify the CLI plugin installation, you can check that it appears in the CLI
+help output or by outputting the plugin version:
+
+```console
+$ docker help | grep ecs
+  ecs*        Docker ECS (Docker Inc., 0.0.1)
+
+$ docker ecs version
+Docker ECS plugin 0.0.1
+```
+
+<!-- FIXME(chris-crone): Link to ECS docs -->
+You are now ready to [start deploying to ECS](http://xxx)