With the changes made in the release v1.0.0 of the plugin framework changes have been made to the types package to simplify custom types. I have looked at the PR and for the most part understand the intentions, but it would be great to get an example of its usage.
There is a minimal example of the usage of a custom type and value in the framework documentation - Plugin Development - Framework: Handling Data - Terraform Concepts | Terraform | HashiCorp Developer
We are currently making some updates to the docs, so this will shortly be moved to a separate page for Custom Types.
There is further information regarding creating custom types and values - Plugin Development - Framework: Attribute Types | Terraform | HashiCorp Developer
These two sources of information will be consolidated in the docs in the near future.