Add some kind of banner to advertise Incubator's game jam beta

[Adzboy]

Above

[Looky1173]

The problem is that currently there are 3 versions of Itinerary, all of them incomplete in some way. There's the old Itinerary at itinerary.eu.org, which I have never finished, the beta version at beta.itinerary.eu.org, which I haven't worked on for some time, and a currently private overhaul of the original Itinerary. It's just too much to maintain, especially because of the different tech stacks and styles.

My plan is to merge all of these into one website which will replace the old Itinerary. Therefore, Itinerary and Incubator will no longer receive updates while I work on a unified version.

@Adzboy If you would like to help out with the code please let me know and I will share the private Itinerary 2.0 GitHub repository with you. Let me know too if you know others who could lend me a hand. 😺