Added tons of opcode documentation, changed license to ISC and a lot of file refactoring.

src/vm/len.c

@@ -1,3 +1,36 @@
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+/**
+* @file len.c
+ * @brief Implements the OP_LEN opcode for getting the length of arrays or strings in the VM.
+ *
+ * This file handles the OP_LEN instruction, which retrieves the length of an array or string.
+ * The array or string is popped from the stack, and the length is pushed back.
+ *
+ * Behavior:
+ * - Pops the array or string from the stack.
+ * - Retrieves the length of the array or string.
+ * - Pushes the length onto the stack.
+ *
+ * Error Handling:
+ * - Exits with an error if the operand is not an array or string.
+ *
+ * Example:
+ * // Bytecode: OP_LEN
+ * // Stack before: ["hello"]
+ * // Stack after: [5]
+ *
+ * @author Johannes Findeisen
+ * @date 2025-10-16
+ */
+
 case OP_LEN: {
     Value a = pop_value(vm);
     int len = 0;