feat: add initial classes for json package

src/com/uulm/marvelous/gamelibrary/json/JSON.java

@@ -0,0 +1,25 @@
+package com.uulm.marvelous.gamelibrary.json;
+
+import jdk.jshell.spi.ExecutionControl;
+
+/** Contains JSON encoding and decoding.
+ */
+public class JSON {
+    /** Deserializes an incoming network message into a {@link MessageStructure}.
+     * @param input The JSON to deserialize.
+     * @return The parsed message.
+     */
+    public static MessageStructure[] parse(String input) throws ExecutionControl.NotImplementedException {
+        //TODO: implement JSON.parse
+        throw new ExecutionControl.NotImplementedException("JSON.parse is not implemented");
+    }
+
+    /** Serializes a {@link MessageStructure} into a JSON string.
+     * @param input The message to serialize.
+     * @return The message as JSON.
+     */
+    public static String stringify(MessageStructure input) throws ExecutionControl.NotImplementedException {
+        //TODO: implement JSON.stringify
+        throw new ExecutionControl.NotImplementedException("JSON.stringify is not implemented");
+    }
+}

src/com/uulm/marvelous/gamelibrary/json/MessageStructure.java

@@ -0,0 +1,25 @@
+package com.uulm.marvelous.gamelibrary.json;
+
+import com.uulm.marvelous.gamelibrary.events.Event;
+
+import java.util.HashMap;
+
+/** Represents a message sent between client and server and contains all possible data.
+ */
+public class MessageStructure {
+    /** The list of {@link Event}s sent inside the message.
+     */
+    public Event[] events;
+
+    /** The checksum of the current game state at the time the message was sent.
+     */
+    public int checksum;
+
+    /** The type of the custom content sent with the message.
+     */
+    public String customContentType;
+
+    /** The decoded contents of the custom content sent.
+     */
+    public HashMap<String, Object> customContent;
+}