SPIGOT-7919: Add API to access current player input

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

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

@@ -0,0 +1,59 @@
+package org.bukkit;
+
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Represents a movement input applied to an entity.
+ */
+@ApiStatus.Experimental
+public interface Input {
+
+    /**
+     * Gets whether a forward input is applied.
+     *
+     * @return forward input
+     */
+    boolean isForward();
+
+    /**
+     * Gets whether a backward input is applied.
+     *
+     * @return backward input
+     */
+    boolean isBackward();
+
+    /**
+     * Gets whether a left input is applied.
+     *
+     * @return left input
+     */
+    boolean isLeft();
+
+    /**
+     * Gets whether a right input is applied.
+     *
+     * @return right input
+     */
+    boolean isRight();
+
+    /**
+     * Gets whether a jump input is applied.
+     *
+     * @return jump input
+     */
+    boolean isJump();
+
+    /**
+     * Gets whether a sneak input is applied.
+     *
+     * @return sneak input
+     */
+    boolean isSneak();
+
+    /**
+     * Gets whether a sprint input is applied.
+     *
+     * @return sprint input
+     */
+    boolean isSprint();
+}