SPIGOT-7850: Add API for Bogged shear state

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/entity/Shearable.java

@@ -0,0 +1,21 @@
+package org.bukkit.entity;
+
+/**
+ * Represents an entity which can be shorn with shears.
+ */
+public interface Shearable {
+
+    /**
+     * Gets whether the entity is in its sheared state.
+     *
+     * @return Whether the entity is sheared.
+     */
+    boolean isSheared();
+
+    /**
+     * Sets whether the entity is in its sheared state.
+     *
+     * @param flag Whether to shear the entity
+     */
+    void setSheared(boolean flag);
+}