SPIGOT-7380: Add PlayerInteractEvent#getClickedPosition and ChiseledBookshelf#getSlot

By: Jishuna <joshl5324@gmail.com>

paper-api/src/main/java/org/bukkit/block/ChiseledBookshelf.java

@@ -2,6 +2,7 @@ package org.bukkit.block;
 
 import org.bukkit.inventory.BlockInventoryHolder;
 import org.bukkit.inventory.ChiseledBookshelfInventory;
+import org.bukkit.util.Vector;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -37,4 +38,16 @@ public interface ChiseledBookshelf extends TileState, BlockInventoryHolder {
      */
     @NotNull
     ChiseledBookshelfInventory getSnapshotInventory();
+
+    /**
+     * Gets the appropriate slot based on a vector relative to this block.<br>
+     * Will return -1 if the given vector is not within the bounds of any slot.
+     * <p>
+     * The supplied vector should only contain components with values between 0.0
+     * and 1.0, inclusive.
+     *
+     * @param position a vector relative to this block
+     * @return the slot under the given vector or -1
+     */
+    int getSlot(@NotNull Vector position);
 }