Add 'vct' in well-known registry

[jtalir]

Type Metadata introduced new well-known URI /.well-known/vct/ in "6.3.1. From a URL in the vct" , but this is not reflected in appendix-A.3 Well-Known URI Registry.

Additionally, using in sentence "Metadata can be retrieved from the URL https:///.well-known/vct/, i.e., by inserting /.well-known/vct after the authority part of the URL." seems to me a little bit confusing as type is considered to refer to whole URI. Maybe use or <uri_suffix>(to include also query and fragment URI components)?

[bc-pi]

Thank you and yes, the registration request is missing and needs to be added. And that sentence could also be improved.

[bc-pi]

Although the use of .well-known for type metadata is being reconsidered #264