feat(rules): expose splash in observation attack reference + AttackResult.splash, document splash weapon rule and JSON schema in README (SRD Throw Splash Weapon)

src/pf1e_simulator/combat.py

@@ -1932,6 +1932,11 @@ class CombatEngine:
                     "range_increment_ft": attack.range_increment_ft,
                     "count": attack.count,
                     "firearm": attack.firearm,
+                    "splash": (
+                        {"damage": attack.splash.damage, "type": attack.splash.type}
+                        if attack.splash is not None
+                        else None
+                    ),
                     "hardness": attack.object_stats()[0],
                     "hit_points": attack.object_stats()[1],
                 }