Add discouraged feature for toGMTString() method

Author: ddbeck

features/date-to-gmt-string.yml

@@ -0,0 +1,11 @@
+name: toGMTString()
+description: The `toGMTSTring()` method of `Date` objects is an alias to the `toUTCString()` method.
+spec: https://tc39.es/ecma262/multipage/additional-ecmascript-features-for-web-browsers.html#sec-date.prototype.togmtstring
+discouraged:
+  according_to:
+    - https://tc39.es/ecma262/multipage/additional-ecmascript-features-for-web-browsers.html#sec-additional-ecmascript-features-for-web-browsers
+  # No `alternatives` becuase it would be `alternatives: [date]`. In the future
+  # it'd be nice to have an internal reference to the `toUTCString()` method
+  # instead.
+compat_features:
+  - javascript.builtins.Date.toGMTString

features/date-to-gmt-string.yml.dist

@@ -0,0 +1,15 @@
+# Generated from: date-to-gmt-string.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+status:
+  baseline: false
+  support:
+    chrome: "1"
+    chrome_android: "18"
+    edge: "12"
+    firefox: "1"
+    firefox_android: "4"
+    safari: "1"
+    safari_ios: "1"
+compat_features:
+  - javascript.builtins.Date.toGMTString