Replace references to NEU with Firmament

src/main/kotlin/moe/nea/firmament/events/ParticleSpawnEvent.kt

@@ -0,0 +1,13 @@
+package moe.nea.firmament.events
+
+import net.minecraft.particle.ParticleEffect
+import net.minecraft.util.math.Vec3d
+
+data class ParticleSpawnEvent(
+    val particleEffect: ParticleEffect,
+    val position: Vec3d,
+    val offset: Vec3d,
+    val longDistance: Boolean,
+) : NEUEvent() {
+    companion object : NEUEventBus<ParticleSpawnEvent>()
+}