Ignore trailing commas where they're not semantically meaningful

sample_files/compare.expected

@@ -283,6 +283,9 @@ sample_files/todomvc_1.gleam sample_files/todomvc_2.gleam
 sample_files/toml_1.toml sample_files/toml_2.toml
 c331bdb54c00b0a5b5a622dbd250042a  -
 
+sample_files/trailing_commas_1.js sample_files/trailing_commas_2.js
+9ca72e199466c75f85d00f4d521e85ff  -
+
 sample_files/trailling_newline_1.yaml sample_files/trailling_newline_2.yaml
 8e37febfec957288576f9c2020cfc4f2  -
 

sample_files/trailing_commas_1.js

@@ -0,0 +1,4 @@
+function foo(x, y) {
+  var z = [1, 2];
+  var zz = {a: 1, b: 2};
+}

sample_files/trailing_commas_2.js

@@ -0,0 +1,13 @@
+function foo(
+  x,
+  y,
+) {
+  var z = [
+    1,
+    2,
+  ];
+  var zz = {
+    a: 1,
+    b: 2,
+  };
+}