Merge pull request 'fuel: tier lava equivalent to crude oil (8000 ticks)' (#50) from fuel/lava-tier-crude into main

Without this entry, lava buckets get the vanilla bucket-burn fallback
of 20000 ticks each — which made lava more powerful than refined
TFMG kerosene/naphtha despite being free and trivially obtainable.

Setting lava to 8000 ticks matches crude_oil exactly: both are the
raw entry-tier fuels you can scoop without any infrastructure, and
the player has to commit to a refining setup to unlock the higher
tiers.

Solid fuels (coal, charcoal, blaze rods, etc.) continue to work via
realisticTrains' chest/barrel pathway -- no datapack entry needed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pack/overrides/world/datapacks/bns-fuel/data/bns/railways_liquid_fuel/lava.json

@@ -0,0 +1,4 @@
+{
+  "fluids": ["minecraft:lava"],
+  "fuel_ticks": 8000
+}