started work on assignment operators

tests/test.pla

@@ -1,7 +1,7 @@
 main = Func(): Int {
-	for (x: Int = 1; x <= 20; x = x + 1;) {
-		$print("i = %i\n", x)
-	}
+	a: Int = 10;
 
-	return x;
+	a += 1;
+
+	return a;
 }