Add readme.

README.md

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+# Composerize Docker image
+
+## What is Composerize?
+
+[Composerize](https://github.com/magicmark/composerize) is a utility that converts any given `docker run` command to its equivalent Docker Compose v2 configuration.
+
+## Usage
+
+To run a container and expose the website at port 8080, run this command:
+
+```sh
+docker run -p "8080:8080" --rm icedream/composerize
+```
+
+Or use this Docker Compose YAML configuration (`docker-compose.yml`) file:
+
+```yaml
+version: '2'
+services:
+    composerize:
+        image: icedream/composerize
+        ports:
+            - '8080:8080'
+```