Rev version number

Note that Core3 has official cert auth

src/idunno.Authentication.Certificate/README.md

@@ -1,13 +1,14 @@
 # idunno.Authentication.Certificate
 
-*This handler is available for ASP.NET Core 2.0 only. Not due to technical reasons, I'm just lazy.*
-
 This project sort of contains an implementation of [Certificate Authentication](https://tools.ietf.org/html/rfc5246#section-7.4.4) for ASP.NET Core. 
 Certificate authentication happens at the TLS level, long before it ever gets to ASP.NET Core, so, more accurately this is an authentication handler
 that validates the certificate and then gives you an event where you can resolve that certificate to a ClaimsPrincipal. 
 
 You **must** [configure your host](#hostConfiguration) for certificate authentication, be it IIS, Kestrel, Azure Web Applications or whatever else you're using.
 
+.NET 3.0 has a supported, shipped version of Certificate Authentication. 
+If you are using .NET Core 3.0 or later please use the [official package](https://docs.microsoft.com/en-us/aspnet/core/security/authentication/certauth?view=aspnetcore-3.1).
+
 ## Getting started
 
 First acquire an HTTPS certificate, apply it and then [configure your host](#hostConfiguration) to require certificates.

version.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://raw.githubusercontent.com/AArnott/Nerdbank.GitVersioning/master/src/NerdBank.GitVersioning/version.schema.json",
-  "version": "2.2.0",
+  "version": "2.2.1",
   "publicReleaseRefSpec": [
     "^refs\/heads\/rel\/.*$"
   ],