Rename exercises dir

Name it instead "topics" so it won't be
strange if some topics included "exercises" directory.

topics/containers/sharing_images.md

@@ -0,0 +1,18 @@
+# Sharing Images
+
+## Requirements
+
+Have at least one image locally (run `podman image ls` to confirm).<br>
+If you don't have images locally, run simply `podman pull httpd`.
+
+## Objectives
+
+1. Choose an image and create an archive out of it
+2. Check the archive size. Is it different than the image size? If yes, what's the difference? If not, why?
+3. Copy the generated archive to a remote host 
+4. Load the image
+5. Verify it was loaded and exists on the remote host
+
+## Solution
+
+Click [here to view the solution](solutions/sharing_images.md)