Experiments (#1174)

Co-authored-by: Andrew Bastin <andrewbastin.k@gmail.com>

lang/en-US.json

@@ -302,5 +302,8 @@
   "select_head_method": "Select HEAD method",
   "select_post_method": "Select POST method",
   "select_put_method": "Select PUT method",
-  "select_delete_method": "Select DELETE method"
+  "select_delete_method": "Select DELETE method",
+  "experiments": "Experiments",
+  "experiments_notice": "This is a collection of experiments we're working on that might turn out to be useful, fun, both, or neither. They're not final and may not be stable, so if something overly weird happens, don't panic. Just turn the dang thing off. Jokes aside, ",
+  "use_experimental_url_bar": "Use experimental URL bar with environment highlighting"
 }