Add crusades

[ChrisNeedham24]

• There should be a list of crusades for players to do for some reward (usually wealth).
• Can be faction or relic based.
• Add a crusades menu as well.
• Crusades should be unlockable based on improvements and/or blessings.

[ChrisNeedham24]

While it would be exciting to do, like #117, this should probably wait for the core functionality to be done, for the most part.

[ChrisNeedham24]

Just had a thought about having conversations with characters occurring in these crusades, providing backstory.

[ChrisNeedham24]

I think we're probably now at a point where the so-called 'core functionality' is done, so this is no longer something that has to wait.

[ChrisNeedham24]

I think it makes sense to wait for #139 before doing this.

[ChrisNeedham24]

The hope is that this will also cover #130.