Introduce ELIXIR Learning Path banner for ELIXIR Learning Paths to distinguish from other Learning Paths

[ac812]

Currently the text for ELIXIR Learning Paths is included in the description field which is stretching the description field and is not looking very well (see image below). The proposal is to include an orange banner before the description of the learning paths, so that we can add the basic text that we have under the ELIXIR Learning Paths heading in this banner.