Include . and ~ in allowed characters for registration tokens

For consistency with the unreserved URL characters in RFC3986

https://www.ietf.org/rfc/rfc3986.html#section-2.3

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

proposals/3231-token-authenticated-registration.md

@@ -19,7 +19,7 @@ endpoint uses the [User-Interactive Authentication API](https://matrix.org/docs/
 A new authentication type `m.login.registration_token` will be defined which requires
 a `token` key to be present in the submitted `auth` dict. The token will be a
 string of no more than 64 characters, and contain only characters matched by the
-regex `[A-Za-z0-9-_]`.
+regex `[A-Za-z0-9._~-]`.
 This will avoid URL encoding issues with the validity checking endpoint, and
 prevent DoS attacks from extremely long tokens.