Add ray tracing and bounding box API

By: blablubbabc <lukas@wirsindwir.de>

paper-api/src/main/java/org/bukkit/FluidCollisionMode.java

@@ -0,0 +1,20 @@
+package org.bukkit;
+
+/**
+ * Determines the collision behavior when fluids get hit during ray tracing.
+ */
+public enum FluidCollisionMode {
+
+    /**
+     * Ignore fluids.
+     */
+    NEVER,
+    /**
+     * Only collide with source fluid blocks.
+     */
+    SOURCE_ONLY,
+    /**
+     * Collide with all fluids.
+     */
+    ALWAYS;
+}