add docker exec script

docs/docker/exec-into-container.md

@@ -0,0 +1,7 @@
+# Exec Into Container
+
+Often it's handy to exec into a container to poke around or run commands. Here's how you can do that:
+
+```bash
+docker run --rm -it --entrypoint /bin/bash <container-name>
+```

docs/docker/index.md

@@ -0,0 +1,3 @@
+# Docker Snippets and Musings
+
+#### [Exec Into Container](./exec-into-container.md)