LibJS: Add ECMA-262 section/title/URL comments almost everywhere

As mentioned on Discord earlier, we'll add these to all new functions
going forward - this is the backfill. Reasons:

- It makes you look at the spec, implementing based on MDN or V8
  behavior is a no-go
- It makes finding the various functions that are non-compliant easier,
  in the future everything should either have such a comment or, if it's
  not from the spec at all, a comment explaining why that is the case
- It makes it easier to check whether a certain abstract operation is
  implemented in LibJS, not all of them use the same name as the spec.
  E.g. RejectPromise() is Promise::reject()
- It makes it easier to reason about vm.arguments(), e.g. when the
  function has a rest parameter
- It makes it easier to see whether a certain function is from a
  proposal or Annex B

Also:

- Add arguments to all functions and abstract operations that already
  had a comment
- Fix some outdated section numbers
- Replace some ecma-international.org URLs with tc39.es

Userland/Libraries/LibJS/Runtime/JSONObject.cpp

@@ -33,6 +33,8 @@ void JSONObject::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.stringify, stringify, 3, attr);
     define_native_function(vm.names.parse, parse, 2, attr);
+
+    // 25.5.3 JSON [ @@toStringTag ], https://tc39.es/ecma262/#sec-json-@@tostringtag
     define_property(vm.well_known_symbol_to_string_tag(), js_string(global_object.heap(), "JSON"), Attribute::Configurable);
 }
 
@@ -117,6 +119,7 @@ String JSONObject::stringify_impl(GlobalObject& global_object, Value value, Valu
     return result;
 }
 
+// 25.5.2 JSON.stringify ( value [ , replacer [ , space ] ] ), https://tc39.es/ecma262/#sec-json.stringify
 JS_DEFINE_NATIVE_FUNCTION(JSONObject::stringify)
 {
     if (!vm.argument_count())
@@ -376,6 +379,7 @@ String JSONObject::quote_json_string(String string)
     return builder.to_string();
 }
 
+// 25.5.1 JSON.parse ( text [ , reviver ] ), https://tc39.es/ecma262/#sec-json.parse
 JS_DEFINE_NATIVE_FUNCTION(JSONObject::parse)
 {
     if (!vm.argument_count())