Add Docker

Added commonly used docker commands to list/start/stop containers.

pages/common/docker.md

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+# docker
+
+> Docker allows you to package an application with all of its
+> dependencies into a standardized unit for software development.
+
+- List of running docker containers
+
+`docker ps`
+
+- List all docker containers (running and stopped)
+
+`docker ps -a`
+
+- Start a container
+
+`docker start {{container}}`
+
+- Stop a container
+
+`docker stop {{container}}`