Implemented register push and pop

src/build/arch/x64/Push.go

@@ -0,0 +1,16 @@
+package x64
+
+import "git.akyoto.dev/cli/q/src/build/cpu"
+
+// PushReg pushes the value inside the register onto the stack.
+func PushReg(code []byte, register cpu.Register) []byte {
+	if register >= 8 {
+		code = append(code, REX(0, 0, 0, 1))
+		register -= 8
+	}
+
+	return append(
+		code,
+		0x50+byte(register),
+	)
+}