more underground structures

Fixed bugs:

Structures are now not able to spawn above ground or floating in the ocean.

New structures:

There is an extra chest dungeon.

There are now new shapes of ore veins.

There are now magma and coal veins.

There are now zombie villager and silverfish spawner dungeons.

There are now drowned spawner dungeons that generate on the bottom of oceans.

There are now fake end portal rooms.

There are now end shrines.

There are now small rooms with a bed.

There are now small tunnels that can generate in your world.