feat(furvm): add return instructions

furvm/include/furvm/instruction.hpp

@@ -27,6 +27,16 @@ enum class instruction_t : byte {
      * @brief Duplicates top element on the stack.
      */
     Duplicate,
+
+    /**
+     * @brief Pops the current call frame.
+     */
+    Return,
+
+    /**
+     * @brief Pops the current call frame and pushes the first element from the previous stack onto the new stack.
+     */
+    ReturnValue,
 };
 
 struct instruction {

furvm/src/main.cpp

@@ -7,7 +7,7 @@
 #include <cstddef>
 
 static constexpr std::array<furvm::byte, 1> s_bytecode = {
-    furvm::byte(furvm::instruction_t::NoOperation),
+    furvm::byte(furvm::instruction_t::Return),
 };
 
 int main(void) {