Fix prettier issues and update read me

README.md

@@ -240,6 +240,10 @@ following attributes:
 
 - `file`: Optional. The generated filename this source map is associated with.
 
+- `x_google_ignoreList`: Optional. An additional extension field which is an array 
+of indices refering to urls in the sources array. This is used to identify third-party
+sources, that the developer might want to avoid when debugging.
+
 The promise of the constructed souce map consumer is returned.
 
 When the `SourceMapConsumer` will no longer be used anymore, you must call its

lib/source-map-consumer.js

@@ -187,7 +187,11 @@ class BasicSourceMapConsumer extends SourceMapConsumer {
       const sourcesContent = util.getArg(sourceMap, "sourcesContent", null);
       const mappings = util.getArg(sourceMap, "mappings");
       const file = util.getArg(sourceMap, "file", null);
-      const x_google_ignoreList = util.getArg(sourceMap, "x_google_ignoreList", null);
+      const x_google_ignoreList = util.getArg(
+        sourceMap,
+        "x_google_ignoreList",
+        null
+      );
 
       // Once again, Sass deviates from the spec and supplies the version as a
       // string rather than a number, so we use loose equality checking here.

test/test-source-map-consumer.js

@@ -88,15 +88,16 @@ exports["test that the `sources` field has the original sources"] =
     map.destroy();
   };
 
-exports["test that the SourceMapConsumer supports the ignoreList"] = async function (assert) {
+exports["test that the SourceMapConsumer supports the ignoreList"] =
+  async function (assert) {
     const map = await new SourceMapConsumer(util.testMapWithIgnoreList);
     const sources = map.sources;
     const ignoreList = map.x_google_ignoreList;
+    assert.equal(ignoreList.length, 1);
     assert.equal(ignoreList[0], 0);
     assert.equal(sources[ignoreList[0]], "/the/root/one.js");
-    assert.equal(ignoreList.length, 1);
     map.destroy();
-}
+  };
 
 exports["test that the source root is reflected in a mapping's source field"] =
   async function (assert) {