Refactor source layout

Introduce compat source sets and move all kotlin sources to the main directory

[no changelog]

src/main/kotlin/events/HandledScreenClickEvent.kt

@@ -0,0 +1,10 @@
+
+
+package moe.nea.firmament.events
+
+import net.minecraft.client.gui.screen.ingame.HandledScreen
+
+data class HandledScreenClickEvent(val screen: HandledScreen<*>, val mouseX: Double, val mouseY: Double, val button: Int) :
+    FirmamentEvent.Cancellable() {
+    companion object : FirmamentEventBus<HandledScreenClickEvent>()
+}