Incompat with Immersive Portals

[andi-makes]

Lighty doesn't seem to get notified about light updates when immersive portals is installed

[andi-makes]

note for future self: Move mixin at the beginning and see if that fixes it

https://github.com/SchmarrnDevs/Lighty/blob/1.20.1/common/src/main/java/dev/schmarrn/lighty/mixin/LightUpdateMixin.java#L28

[andi-makes]

With commit 3b6b403, the issue gets reduced a little bit, any block update triggers a recomputation of that subchunk, but only that subchunk. So if you place a torch at the border of a chunk, no neighboring chunks get updated.

Didn't investigate the mixin location.

[andi-makes]

Conditionally mixin into https://github.com/iPortalTeam/ImmersivePortalsMod/blob/1.20.1/imm_ptl_core/src/main/java/qouteall/imm_ptl/core/chunk_loading/ImmPtlClientChunkMap.java#L233 if Immersive Portals is loaded, this should fix the issue completely