Katacoda supports linking to images in the assets folder. Update our
existing links to use this approach instead of using the GitHub 'raw'
URLs as this gives us greater portability for the tutorials and ensures
the correct version of the images is loaded even if we stop loading content
from the `master` branch in future.

- Moved over Brandow Walker's dashboard tutorial
- Created the basic pipeline tutorial
Signed-off-by: NJJ Asghar <jjasghar@gmail.com>
Co-authored-by: NBrandon Walker <bcwalker@ibm.com>