fix: missing nested expression braces

TODO

@@ -1,5 +1,4 @@
 # Bugs
-- Generated nested expressions should include braces
 
 # Cleanups
 - Improve error reporting (See ./util/string_util::highlight_position_in_file)

examples/playground.sb

@@ -1,9 +1,5 @@
 fn main() {
 
-    let arr = [[11, 12, 13], [21, 22, 23], [31, 32, 33]]
-    for i in arr {
-        for j in i {
-            println(j)
-        }
-    }
+    let x = (1 + (2 * 3))
+    print(x)
 }

src/generator/js.rs

@@ -244,7 +244,7 @@ fn generate_bin_op(left: Expression, op: BinOp, right: Expression) -> String {
         BinOp::Subtraction => "-",
     };
     format!(
-        "{l} {op} {r}",
+        "({l} {op} {r})",
         l = generate_expression(left),
         op = op_str,
         r = generate_expression(right)