Add a validation guarantee to curated CDDL extracts (#1422)

* Add a validation guarantee to curated CDDL extracts

This leverages CDDL validation in Strudy to provide a validation guarantee to
curated CDDL extracts.

A `cddlpatches` folder, which will hopefully remain empty, gets added so that
we may temporarily patch CDDL extracts that become invalid.

* Adjust list of ignorable Web IDL anomalies

Bumping the version of Strudy brings new Web IDL anomaly types:
- `noEvent` needs events data that is not included in the data we pass to the
study function. It must be ignored.
- `urlType` is new and we probably don't want to block curation because of it,
at least for now (or we're going to have a lot of patching to do...)

README.md

@@ -92,7 +92,9 @@ Data curation brings the following guarantees.
 
 ### CDDL extracts
 
-The CDDL extracts currently come with no guarantee whatsoever and may be invalid. Tracked in [#1417](https://github.com/w3c/webref/issues/1417).
+- All CDDL files pass CDDL analysis by the version of [Strudy](https://github.com/w3c/strudy) referenced in `package.json`. Said differently, all CDDL files can be parsed by the version of [cddlparser](https://github.com/tidoust/cddlparser) referenced by Strudy.
+
+The CDDL extracts are not released in an NPM package for the time being.
 
 ## Known consumers
 

ed/cddlpatches/README.md

@@ -0,0 +1,5 @@
+# CDDL patches
+
+These are patches applied to the CDDL extracts scraped from specs. These patches can break as specs are updated and thus need ongoing maintenance.
+
+For details on how to create and update patches, please see the [Web IDL patches documentation](../idlpatches/README.md)