surfacing Learn by example topics to top level of Docker Engine docs

fixing links after moving surfacing tutorials

fixing more links for the newly located tutorials

Signed-off-by: Victoria Bialas <victoria.bialas@docker.com>
Upstream-commit: 8eca8089fa35f652060e86906166dabc42e556f8
Component: engine

components/engine/docs/tutorials/index.md

@@ -0,0 +1,23 @@
+<!--[metadata]>
++++
+aliases = [
+"/engine/userguide/containers/",
+]
+title = "Learn by example"
+description = "Explains how to work with containers"
+keywords = ["docker, introduction, documentation, about, technology, docker.io, user, guide, user's, manual, platform, framework, home,  intro"]
+[menu.main]
+identifier="engine_learn"
+parent = "engine_use"
+weight="-80"
++++
+<![end-metadata]-->
+
+# Learn by example
+
+* [Hello world in a container](dockerizing.md)
+* [Run a simple application](usingdocker.md)
+* [Build your own images](dockerimages.md)
+* [Network containers](networkingcontainers.md)
+* [Manage data in containers](dockervolumes.md)
+* [Store images on Docker Hub](dockerrepos.md)