Allow end portal frames to drop as items using movableEndPortalFrames

[Gilly7CE]

Following #52, it was found that the blocks would not drop as items when pushed by a piston and tnt explodes as soon as they're pushed.

This improvement/feature would allow for them to drop as items when pushed by a piston. Likely will require a mixin targeting the PistonBlockEntity class.

This should not be its own separate rules but instead to extend the existing "movable" rules to have a third allow value. The allowed values should be:

• true
• false (default)
• dropAsItemOnExplosion

This won't be included in v1.0.0 but a future version. Likely v1.1.0.

[Gilly7CE]

Injection method should be PistonExtensionBlock.getDroppedStacks with a target for pistonBlockEntity.getPushedBlock().getDroppedStacks(builder); This is where a pistonBlockEntity has dropped stacks from.

[Gilly7CE]

This would be a minor version update. Old value for the rule is parsed correctly so it is not a breaking change.

[Gilly7CE]

Decided this can be included in v1.0.0 but with end portal frames only. Spawners is kind of pointless as no nbt data can be saved.

[Gilly7CE]

Spawners can be revisited in the future, have a potential idea but not too bothered for v1.0.0