Propose a way to simplify sample map creation

[shanayyy]

Thanks for your amazing work, this will definitely save people a lot of time.😃

The sample map is easy to use, but it is difficult to configure on some of the more complex tilesets, such as this one: Asset link

To generate roads and rivers, quite a bit of configuration is required here. I know there is a complete_matrices option, but if there is a bad sample configuration, it is hard to see what is missed, so I just do it all manually. This is just a small sample and I may have missed many：

It can be seen that configuring a complete rule sample requires a lot of work and is difficult to track. So I propose that the rules can be generated from the terrain set of TileSet. https://docs.godotengine.org/en/stable/tutorials/2d/using_tilesets.html#creating-terrain-sets-autotiling

Each tile has a terrain, and has saved the terrains it can be adjacent to, so I think there is enough information to generate rules. If this is implemented, most configurations of the sample map should be avoided. What do you think?